Human antibodies to pd-1

ABSTRACT

The present invention provides antibodies that bind to the T-cell co-inhibitor programmed death-1 (PD-1) protein, and methods of use. In various embodiments of the invention, the antibodies are fully human antibodies that bind to PD-1. In certain embodiments, the present invention provides multi-specific antigen-binding molecules comprising a first binding specificity that binds to PD-1 and a second binding specificity that binds to an autoimmune tissue antigen, another T-cell co-inhibitor, an Fc receptor, or a T-cell receptor. In some embodiments, the antibodies of the invention are useful for inhibiting or neutralizing PD-1 activity, thus providing a means of treating a disease or disorder such as cancer or a chronic viral infection. In other embodiments, the antibodies are useful for enhancing or stimulating PD-1 activity, thus providing a means of treating, for example, an autoimmune disease or disorder.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/905,685 filed Feb. 26, 2018, which is a continuation of U.S. patentapplication Ser. No. 14/603,776 filed Jan. 23, 2015 (now U.S. Pat. No.9,987,500), which claims the benefit of priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 62/014,181 filed Jun.19, 2014 and U.S. Provisional Patent Application No. 61/930,576 filedJan. 23, 2014, the disclosures of all of which are hereby incorporatedby reference in their entireties.

FIELD OF THE INVENTION

The present invention is related to human antibodies and antigen-bindingfragments of human antibodies that specifically bind to theimmunomodulatory receptor programmed death-1 (PD-1), and therapeutic anddiagnostic methods of using those antibodies.

STATEMENT OF RELATED ART

Programmed death-1 (PD-1) (also called CD279) is a 288 amino acidprotein receptor expressed on activated T-cells and B-cells, naturalkiller cells and monocytes. PD-1 is a member of the CD28/CTLA-4(cytotoxic T lymphocyte antigen)/ICOS (inducible co-stimulator) familyof T-cell co-inhibitory receptors (Chen et al 2013, Nat. Rev. Immunol.13: 227-242). The primary function of PD-1 is to attenuate the immuneresponse (Riley 2009, Immunol. Rev. 229: 114-125). PD-1 has two ligands,PD-ligand1 (PD-L1) and PD-L2. PD-L1 (CD274, B7H1) is expressed widely onboth lymphoid and non-lymphoid tissues such as CD4 and CD8 T-cells,macrophage lineage cells, peripheral tissues as well as on tumor cells,virally-infected cells and autoimmune tissue cells. PD-L2 (CD273, B7-DC)has a more restricted expression than PD-L1, being expressed onactivated dendritic cells and macrophages (Dong et al 1999, NatureMed.). PD-L1 is expressed in most human cancers, including melanoma,glioma, non-small cell lung cancer, squamous cell carcinoma of head andneck, leukemia, pancreatic cancer, renal cell carcinoma, andhepatocellular carcinoma, and may be inducible in nearly all cancertypes (Zou and Chen 2008, Nat. Rev. Immunol. 8: 467-77). PD-1 binding toits ligands results in decreased T-cell proliferation and cytokinesecretion, compromising humoral and cellular immune responses indiseases such as cancer, viral infection and autoimmune disease.Blockade of PD-1 binding to reverse immunosuppression has been studiedin autoimmune, viral and tumor immunotherapy (Ribas 2012, NEJM 366:2517-2519; Watanabe et al 2012, Clin. Dev. Immunol. Volume 2012, ArticleID: 269756; Wang et al 2013, J. Viral Hep. 20: 27-39).

T-cell co-stimulatory and co-inhibitory molecules (collectively namedco-signaling molecules) play a crucial role in regulating T-cellactivation, subset differentiation, effector function and survival (Chenet al 2013, Nature Rev. Immunol. 13: 227-242). Following recognition ofcognate peptide-MHC complexes on antigen-presenting cells by the T-cellreceptor, co-signaling receptors co-localize with T-cell receptors atthe immune synapse, where they synergize with TCR signaling to promoteor inhibit T-cell activation and function (Flies et al 2011, Yale J.Biol. Med. 84: 409-421). The ultimate immune response is regulated by abalance between co-stimulatory and co-inhibitory signals (“immunecheckpoints”) (Pardoll 2012, Nature 12: 252-264). PD-1 functions as onesuch ‘immune checkpoint’ in mediating peripheral T-cell tolerance and inavoiding autoimmunity. PD-1 binds to PD-L1 or PD-L2 and inhibits T-cellactivation. The ability of PD1 to inhibit T-cell activation is exploitedby chronic viral infections and tumors to evade immune response. Inchronic viral infections, PD-1 is highly expressed on virus-specificT-cells and these T-cells become “exhausted” with loss of effectorfunctions and proliferative capacity (Freeman 2008, PNAS 105:10275-10276). PD-L1 is expressed on a wide variety of tumors and studieson animal models have shown that PD-L1 on tumors inhibits T-cellactivation and lysis of tumor cells and may lead to increased death oftumor-specific T-cells. The PD-1: PD-L1 system also plays an importantrole in induced T-regulatory (Treg) cell development and in sustainingTreg function (Francisco et al 2010, Immunol. Rev. 236: 219-242).

Since PD-1 plays an important role in autoimmunity, tumor immunity andinfectious immunity, it is an ideal target for immunotherapy. BlockingPD-1 with antagonists, including monoclonal antibodies, has been studiedin treatments of cancer and chronic viral infections (Sheridan 2012,Nature Biotechnology 30: 729-730).

Monoclonal antibodies to PD-1 are known in the art and have beendescribed, for example, in US Patent/Publication Nos. 8008449, 8168757,20110008369, 20130017199, 20130022595, and in WO2006121168,WO20091154335, WO2012145493, WO2013014668, WO2009101611, EP2262837, andEP2504028.

BRIEF SUMMARY OF THE INVENTION

The present invention provides antibodies and antigen-binding fragmentsthereof that bind PD-1. The antibodies of the present invention areuseful, inter alia, for targeting T cells expressing PD-1, and formodulating PD-1 activity. In certain embodiments, the antibodies of theinvention are useful for inhibiting or neutralizing PD-1 activity and/orfor stimulating T cell activation, e.g., under circumstances where Tcell-mediated killing is beneficial or desirable. In alternateembodiments, the antibodies enhance PD-1 binding and/or activity and maybe used to inhibit T-cell activation. The anti-PD-1 antibodies of theinvention, or antigen-binding portions thereof, may be included as partof a multi-specific antigen-binding molecule, for example, to modulatethe immune response and/or to target the antibodies to a specific celltype, such as a tumor cell, an autoimmune tissue cell or a virallyinfected cell. The antibodies are useful in treating a disease ordisorder such as cancer, viral infection and autoimmune disease.

The antibodies of the invention can be full-length (for example, an IgG1or IgG4 antibody) or may comprise only an antigen-binding portion (forexample, a Fab, F(ab)₂ or scFv fragment), and may be modified to affectfunctionality, e.g., to eliminate residual effector functions (Reddy etal., 2000, J. Immunol. 164:1925-1933). In certain embodiments, theantibodies may be bispecific.

In a first aspect, the present invention provides isolated recombinantmonoclonal antibodies or antigen-binding fragments thereof that bindspecifically to PD-1. In certain embodiments, the antibodies are fullyhuman. Exemplary anti-PD-1 antibodies of the present invention arelisted in Tables 1-3 herein. Table 1 sets forth the amino acid sequenceidentifiers of the heavy chain variable regions (HCVRs), light chainvariable regions (LCVRs), heavy chain complementarity determiningregions (HCDR1, HCDR2 and HCDR3), and light chain complementaritydetermining regions (LCDR1, LCDR2 and LCDR3) of the exemplary anti-PD-1antibodies. Table 2 sets forth the nucleic acid sequence identifiers ofthe HCVRs, LCVRs, HCDR1, HCDR2 HCDR3, LCDR1, LCDR2 and LCDR3 of theexemplary anti-PD-1 antibodies. Table 3 sets forth the amino acidsequence identifiers of heavy chain and light chain sequences ofexemplary anti-PD-1 antibodies.

The present invention provides antibodies, or antigen-binding fragmentsthereof, comprising an HCVR comprising an amino acid sequence selectedfrom any of the HCVR amino acid sequences listed in Table 1, or asubstantially similar sequence thereof having at least 90%, at least95%, at least 98% or at least 99% sequence identity thereto.

The present invention also provides antibodies, or antigen-bindingfragments thereof, comprising an LCVR comprising an amino acid sequenceselected from any of the LCVR amino acid sequences listed in Table 1, ora substantially similar sequence thereof having at least 90%, at least95%, at least 98% or at least 99% sequence identity thereto.

The present invention also provides antibodies, or antigen-bindingfragments thereof, comprising an HCVR and an LCVR amino acid sequencepair (HCVR/LCVR) comprising any of the HCVR amino acid sequences listedin Table 1 paired with any of the LCVR amino acid sequences listed inTable 1. According to certain embodiments, the present inventionprovides antibodies, or antigen-binding fragments thereof, comprising anHCVR/LCVR amino acid sequence pair contained within any of the exemplaryanti-PD-1 antibodies listed in Table 1. In certain embodiments, theHCVR/LCVR amino acid sequence pair is selected from the group consistingof SEQ ID NOs: 2/10, 18/26, 34/42, 50/58, 66/74, 82/90, 98/106, 114/122,130/138, 146/154, 162/170, 178/186, 194/202, 210/202, 218/202, 226/202,234/202, 242/202, 250/202, 258/202, 266/202, 274/202, 282/202, 290/202,298/186, 306/186 and 314/186. In certain embodiments, the HCVR/LCVRamino acid sequence pair is selected from one of SEQ ID NOs: 130/138(e.g., H2M7795N), 162/170 (e.g., H2M7798N), 234/202 (e.g., H4xH9048P),or 314/186 (e.g., H4xH9008P).

The present invention also provides antibodies, or antigen-bindingfragments thereof, comprising a heavy chain CDR1 (HCDR1) comprising anamino acid sequence selected from any of the HCDR1 amino acid sequenceslisted in Table 1 or a substantially similar sequence thereof having atleast 90%, at least 95%, at least 98% or at least 99% sequence identity.

The present invention also provides antibodies, or antigen-bindingfragments thereof, comprising a heavy chain CDR2 (HCDR2) comprising anamino acid sequence selected from any of the HCDR2 amino acid sequenceslisted in Table 1 or a substantially similar sequence thereof having atleast 90%, at least 95%, at least 98% or at least 99% sequence identity.

The present invention also provides antibodies, or antigen-bindingfragments thereof, comprising a heavy chain CDR3 (HCDR3) comprising anamino acid sequence selected from any of the HCDR3 amino acid sequenceslisted in Table 1 or a substantially similar sequence thereof having atleast 90%, at least 95%, at least 98% or at least 99% sequence identity.

The present invention also provides antibodies, or antigen-bindingfragments thereof, comprising a light chain CDR1 (LCDR1) comprising anamino acid sequence selected from any of the LCDR1 amino acid sequenceslisted in Table 1 or a substantially similar sequence thereof having atleast 90%, at least 95%, at least 98% or at least 99% sequence identity.

The present invention also provides antibodies, or antigen-bindingfragments thereof, comprising a light chain CDR2 (LCDR2) comprising anamino acid sequence selected from any of the LCDR2 amino acid sequenceslisted in Table 1 or a substantially similar sequence thereof having atleast 90%, at least 95%, at least 98% or at least 99% sequence identity.

The present invention also provides antibodies, or antigen-bindingfragments thereof, comprising a light chain CDR3 (LCDR3) comprising anamino acid sequence selected from any of the LCDR3 amino acid sequenceslisted in Table 1 or a substantially similar sequence thereof having atleast 90%, at least 95%, at least 98% or at least 99% sequence identity.

The present invention also provides antibodies, or antigen-bindingfragments thereof, comprising an HCDR3 and an LCDR3 amino acid sequencepair (HCDR3/LCDR3) comprising any of the HCDR3 amino acid sequenceslisted in Table 1 paired with any of the LCDR3 amino acid sequenceslisted in Table 1. According to certain embodiments, the presentinvention provides antibodies, or antigen-binding fragments thereof,comprising an HCDR3/LCDR3 amino acid sequence pair contained within anyof the exemplary anti-PD-1 antibodies listed in Table 1. In certainembodiments, the HCDR3/LCDR3 amino acid sequence pair is selected fromthe group consisting of SEQ ID NOs: 136/144 (e.g., H2M7795N), 168/176(e.g., H2M7798N), 240/208 (e.g., H4xH9048P), and 320/192 (e.g.,H4xH9008P).

The present invention provides antibodies, or antigen-binding fragmentsthereof, comprising a heavy chain comprising an amino acid sequenceselected from any of the HC amino acid sequences listed in Table 3, or asubstantially similar sequence thereof having at least 90%, at least95%, at least 98% or at least 99% sequence identity thereto.

The present invention also provides antibodies, or antigen-bindingfragments thereof, comprising a light chain comprising an amino acidsequence selected from any of the LC amino acid sequences listed inTable 3, or a substantially similar sequence thereof having at least90%, at least 95%, at least 98% or at least 99% sequence identitythereto.

The present invention also provides antibodies, or antigen-bindingfragments thereof, comprising a HC and a LC amino acid sequence pair(HC/LC) comprising any of the HC amino acid sequences listed in Table 3paired with any of the LC amino acid sequences listed in Table 3.According to certain embodiments, the present invention providesantibodies, or antigen-binding fragments thereof, comprising an HC/LCamino acid sequence pair contained within any of the exemplary anti-PD-1antibodies listed in Table 3. In certain embodiments, the HC/LC aminoacid sequence pair is selected from the group consisting of SEQ ID NOs:330/331, 332/333, 334/335, and 336/337.

The present invention also provides antibodies, or antigen-bindingfragments thereof, comprising a set of six CDRs (i.e.,HCDR1-HCDR2-HCDR3-LCDR1-LCDR2-LCDR3) contained within any of theexemplary anti-PD-1 antibodies listed in Table 1. In certainembodiments, the HCDR1-HCDR2-HCDR3-LCDR1-LCDR2-LCDR3 amino acid sequenceset is selected from the group consisting of SEQ ID NOs:132-134-136-140-142-144 (e.g., H2M7795N); 164-166-168-172-174-176 (e.g.,H2M7798N); 236-238-240-204-206-208 (e.g., H4xH9048P); and316-318-320-188-190-192 (e.g., H4xH9008P).

In a related embodiment, the present invention provides antibodies, orantigen-binding fragments thereof, comprising a set of six CDRs (i.e.,HCDR1-HCDR2-HCDR3-LCDR1-LCDR2-LCDR3) contained within an HCVR/LCVR aminoacid sequence pair as defined by any of the exemplary anti-PD-1antibodies listed in Table 1. For example, the present inventionincludes antibodies, or antigen-binding fragments thereof, comprisingthe HCDR1-HCDR2-HCDR3-LCDR1-LCDR2-LCDR3 amino acid sequences setcontained within an HCVR/LCVR amino acid sequence pair selected from thegroup consisting of SEQ ID NOs: 130/138 (e.g., H2M7795N); 162/170 (e.g.,H2M7798N); 234/202 (e.g., H4xH9048P); and 314/186 (e.g., H4xH9008P).Methods and techniques for identifying CDRs within HCVR and LCVR aminoacid sequences are well known in the art and can be used to identifyCDRs within the specified HCVR and/or LCVR amino acid sequencesdisclosed herein. Exemplary conventions that can be used to identify theboundaries of CDRs include, e.g., the Kabat definition, the Chothiadefinition, and the AbM definition. In general terms, the Kabatdefinition is based on sequence variability, the Chothia definition isbased on the location of the structural loop regions, and the AbMdefinition is a compromise between the Kabat and Chothia approaches.See, e.g., Kabat, “Sequences of Proteins of Immunological Interest,”National Institutes of Health, Bethesda, Md. (1991); Al-Lazikani et al.,J. Mol. Biol. 273:927-948 (1997); and Martin et al., Proc. Natl. Acad.Sci. USA 86:9268-9272 (1989). Public databases are also available foridentifying CDR sequences within an antibody.

The present invention includes anti-PD-1 antibodies having a modifiedglycosylation pattern. In some embodiments, modification to removeundesirable glycosylation sites may be useful, or an antibody lacking afucose moiety present on the oligosaccharide chain, for example, toincrease antibody dependent cellular cytotoxicity (ADCC) function (seeShield et al. (2002) JBC 277:26733). In other applications, modificationof galactosylation can be made in order to modify complement dependentcytotoxicity (CDC).

The present invention also provides for antibodies and antigen-bindingfragments thereof that compete for specific binding to PD-1 with anantibody or antigen-binding fragment thereof comprising the CDRs of aHCVR and the CDRs of a LCVR, wherein the HCVR and LCVR each has an aminoacid sequence selected from the HCVR and LCVR sequences listed in Table1.

The present invention also provides isolated antibodies andantigen-binding fragments thereof that block PD-1 binding to PD-L1 orPD-L2. In some embodiments, the antibody or antigen-binding fragmentthereof that blocks PD-1 binding to PD-L1 may bind to the same epitopeon PD-1 as PD-L1 or may bind to a different epitope on PD-1 as PD-L1.

In alternate embodiments, the present invention provides antibodies andantigen-binding fragments thereof that stimulate PD-1 binding to PD-L1.In certain embodiments, the present invention provides isolatedantibodies or antigen-binding fragments thereof that bind PD-1, whereinthe antibodies or antigen-binding fragments thereof enhance PD-1 bindingto PD-L1. In some embodiments, the isolated antibodies orantigen-binding fragments thereof comprise the CDRs of a HCVR, whereinthe HCVR has an amino acid sequence selected from the group consistingof SEQ ID NOs: 2, 98, and 250; and the CDRs of a LCVR, wherein the LCVRhas an amino acid sequence selected from the group consisting of SEQ IDNOs: 10, 106, and 202. In some embodiments, the isolated antibodies orantigen-binding fragments thereof comprise an HCVR/LCVR amino acidsequence pair selected from the group consisting of SEQ ID NOs: 2/10(e.g., H1M7789N), 98/106 (e.g., H2M7791N), and 250/202 (e.g.,H4H9068P2).

The present invention also provides antibodies and antigen-bindingfragments thereof that bind specifically to PD-1 from human or otherspecies. In certain embodiments, the antibodies may bind to human PD-1and/or to cynomolgus PD-1.

The present invention also provides antibodies and antigen-bindingfragments thereof that cross-compete for binding to PD-1 with areference antibody or antigen-binding fragment thereof comprising theCDRs of a HCVR and the CDRs of a LCVR, wherein the HCVR and LCVR eachhas an amino acid sequence selected from the HCVR and LCVR sequenceslisted in Table 1.

In one embodiment, the invention provides an isolated antibody orantigen-binding fragment that has one or more of the followingcharacteristics: (a) blocks the binding of PD-1 to PD-L1 or PD-L2; (b)binds specifically to human PD-1 and/or cynomolgus PD-1; (c) blocksPD-1-induced T-cell down regulation and rescues T-cell signaling; (d)suppresses tumor growth and increases survival in subjects with coloncancer; (e) inhibits T-cell proliferation in a mixed lymphocyte reaction(MLR) assay; and (f) increases IL-2 and/or interferon-gamma secretion ina MLR assay.

In some embodiments, the antibody or antigen binding fragment thereofmay bind specifically to PD-1 in an agonist manner, i.e., it may enhanceor stimulate PD-1 binding and/or activity; in other embodiments, theantibody may bind specifically to PD-1 in an antagonist manner, i.e., itmay block PD-1 from binding to its ligand.

In certain embodiments, the antibodies or antigen-binding fragments ofthe present invention are bispecific comprising a first bindingspecificity to PD-1 and a second binding specificity for a second targetepitope. The second target epitope may be another epitope on PD-1 or ona different protein. In certain embodiments, the target epitope may beon a different cell including a different T-cell, a B-cell, a tumorcell, an autoimmune tissue cell or a virally infected cell.

In a second aspect, the present invention provides nucleic acidmolecules encoding anti-PD-1 antibodies or portions thereof. Forexample, the present invention provides nucleic acid molecules encodingany of the HCVR amino acid sequences listed in Table 1; in certainembodiments the nucleic acid molecule comprises a polynucleotidesequence selected from any of the HCVR nucleic acid sequences listed inTable 2, or a substantially similar sequence thereof having at least90%, at least 95%, at least 98% or at least 99% sequence identitythereto.

The present invention also provides nucleic acid molecules encoding anyof the LCVR amino acid sequences listed in Table 1; in certainembodiments the nucleic acid molecule comprises a polynucleotidesequence selected from any of the LCVR nucleic acid sequences listed inTable 2, or a substantially similar sequence thereof having at least90%, at least 95%, at least 98% or at least 99% sequence identitythereto.

The present invention also provides nucleic acid molecules encoding anyof the HCDR1 amino acid sequences listed in Table 1; in certainembodiments the nucleic acid molecule comprises a polynucleotidesequence selected from any of the HCDR1 nucleic acid sequences listed inTable 2, or a substantially similar sequence thereof having at least90%, at least 95%, at least 98% or at least 99% sequence identitythereto.

The present invention also provides nucleic acid molecules encoding anyof the HCDR2 amino acid sequences listed in Table 1; in certainembodiments the nucleic acid molecule comprises a polynucleotidesequence selected from any of the HCDR2 nucleic acid sequences listed inTable 2, or a substantially similar sequence thereof having at least90%, at least 95%, at least 98% or at least 99% sequence identitythereto.

The present invention also provides nucleic acid molecules encoding anyof the HCDR3 amino acid sequences listed in Table 1; in certainembodiments the nucleic acid molecule comprises a polynucleotidesequence selected from any of the HCDR3 nucleic acid sequences listed inTable 2, or a substantially similar sequence thereof having at least90%, at least 95%, at least 98% or at least 99% sequence identitythereto.

The present invention also provides nucleic acid molecules encoding anyof the LCDR1 amino acid sequences listed in Table 1; in certainembodiments the nucleic acid molecule comprises a polynucleotidesequence selected from any of the LCDR1 nucleic acid sequences listed inTable 2, or a substantially similar sequence thereof having at least90%, at least 95%, at least 98% or at least 99% sequence identitythereto.

The present invention also provides nucleic acid molecules encoding anyof the LCDR2 amino acid sequences listed in Table 1; in certainembodiments the nucleic acid molecule comprises a polynucleotidesequence selected from any of the LCDR2 nucleic acid sequences listed inTable 2, or a substantially similar sequence thereof having at least90%, at least 95%, at least 98% or at least 99% sequence identitythereto.

The present invention also provides nucleic acid molecules encoding anyof the LCDR3 amino acid sequences listed in Table 1; in certainembodiments the nucleic acid molecule comprises a polynucleotidesequence selected from any of the LCDR3 nucleic acid sequences listed inTable 2, or a substantially similar sequence thereof having at least90%, at least 95%, at least 98% or at least 99% sequence identitythereto.

The present invention also provides nucleic acid molecules encoding anHCVR, wherein the HCVR comprises a set of three CDRs (i.e.,HCDR1-HCDR2-HCDR3), wherein the HCDR1-HCDR2-HCDR3 amino acid sequenceset is as defined by any of the exemplary anti-PD-1 antibodies listed inTable 1.

The present invention also provides nucleic acid molecules encoding anLCVR, wherein the LCVR comprises a set of three CDRs (i.e.,LCDR1-LCDR2-LCDR3), wherein the LCDR1-LCDR2-LCDR3 amino acid sequenceset is as defined by any of the exemplary anti-PD-1 antibodies listed inTable 1.

The present invention also provides nucleic acid molecules encoding bothan HCVR and an LCVR, wherein the HCVR comprises an amino acid sequenceof any of the HCVR amino acid sequences listed in Table 1, and whereinthe LCVR comprises an amino acid sequence of any of the LCVR amino acidsequences listed in Table 1. In certain embodiments, the nucleic acidmolecule comprises a polynucleotide sequence selected from any of theHCVR nucleic acid sequences listed in Table 2, or a substantiallysimilar sequence thereof having at least 90%, at least 95%, at least 98%or at least 99% sequence identity thereto, and a polynucleotide sequenceselected from any of the LCVR nucleic acid sequences listed in Table 2,or a substantially similar sequence thereof having at least 90%, atleast 95%, at least 98% or at least 99% sequence identity thereto. Incertain embodiments according to this aspect of the invention, thenucleic acid molecule encodes an HCVR and LCVR, wherein the HCVR andLCVR are both derived from the same anti-PD-1 antibody listed in Table1.

The present invention provides nucleic acid molecules encoding any ofthe heavy chain amino acid sequences listed in Table 3. The presentinvention also provides nucleic acid molecules encoding any of the lightchain amino acid sequences listed in Table 3.

The present invention also provides nucleic acid molecules encoding bothheavy chain (HC) and a light chain (LC), wherein the HC comprises anamino acid sequence of any of the HC amino acid sequences listed inTable 3, and wherein the LC comprises an amino acid sequence of any ofthe LC amino acid sequences listed in Table 3.

In a related aspect, the present invention provides recombinantexpression vectors capable of expressing a polypeptide comprising aheavy or light chain variable region of an anti-PD-1 antibody. Forexample, the present invention includes recombinant expression vectorscomprising any of the nucleic acid molecules mentioned above, i.e.,nucleic acid molecules encoding any of the HCVR, LCVR, and/or CDRsequences as set forth in Table 1. The present invention also providesrecombinant expression vectors capable of expressing a polypeptidecomprising a heavy or light chain of an anti-PD-1 antibody. For example,the present invention includes recombinant expression vectors comprisingany of the nucleic acid molecules mentioned above, i.e., nucleic acidmolecules encoding any of the heavy chain or light chain sequences asset forth in Table 3. Also included within the scope of the presentinvention are host cells into which such vectors have been introduced,as well as methods of producing the antibodies or portions thereof byculturing the host cells under conditions permitting production of theantibodies or antibody fragments, and recovering the antibodies andantibody fragments so produced.

In a third aspect, the present invention provides multi-specificantigen-binding molecules and antigen-binding fragments thereofcomprising a first antigen-binding specificity that binds specificallyto PD-1 and a second antigen-binding specificity that binds specificallyto an antigen selected from the group consisting of a tumorcell-specific antigen, an autoimmune tissue-specific antigen, aninfected-cell-specific antigen, a T-cell co-inhibitor, a T-cellreceptor, a Fc receptor, PD-L1, and PD-1. In certain embodiments, thefirst antigen-binding specificity may comprise three CDRs derived from aHCVR with an amino acid sequence selected from the HCVR sequences inTable 1 and three CDRs derived from a LCVR with an amino acid sequenceselected from the LCVR sequences in Table 1. In one embodiment, thefirst antigen-binding specificity may comprise the extracellular domainof PD-L1. The second antigen-binding specificity may target an antigenon the same cell as PD-1 or on a different cell of the same tissue typeor of a different tissue type. For example, the multi-specificantigen-binding molecule may bind to a T-cell wherein the firstantigen-binding specificity may bind specifically to PD-1 and the secondantigen-binding specificity may bind to a T-cell receptor on the T-cell.Alternatively, in another embodiment, the first antigen-bindingspecificity may bind specifically to PD-1 on a T-cell and the secondantigen-binding specificity may be targeted to an antigen/receptor on aB-cell or a macrophage or antigen-presenting cell. In certainembodiments, the second antigen-binding specificity may be directed toan antigen associated with an autoimmune tissue. In one embodiment, thefirst antigen-binding specificity may comprise an extracellular domainof PD-L1 and the second antigen-binding specificity may bind to anotherepitope on PD-1. In certain embodiments, the first antigen-bindingspecificity binds to PD-1 with a lower affinity, for example, with aK_(D) more than 10⁻⁷ M, more than 10⁻⁶ M, more than 10⁻⁵ M, or more than10⁻⁴ M.

In a fourth aspect, the invention provides a pharmaceutical compositioncomprising a recombinant human antibody or fragment thereof whichspecifically binds PD-1 and a pharmaceutically acceptable carrier. In arelated aspect, the invention features a composition which is acombination of an anti-PD-1 antibody and a second therapeutic agent. Inone embodiment, the second therapeutic agent is any agent that isadvantageously combined with an anti-PD-1 antibody. Exemplary agentsthat may be advantageously combined with an anti-PD-1 antibody include,without limitation, other agents that bind and/or modulate PD-1signaling (including other antibodies or antigen-binding fragmentsthereof, etc.) and/or agents which do not directly bind PD-1 butnonetheless modulate immune cell activation. Additional combinationtherapies and co-formulations involving the anti-PD-1 antibodies of thepresent invention are disclosed elsewhere herein.

In a fifth aspect, the invention provides methods to modulate the immuneresponse in a subject, the method comprising administering atherapeutically effective amount of an anti-PD-1 antibody orantigen-binding fragment thereof of the invention to the subject in needthereof. In certain embodiments, the invention provides methods toenhance the immune response in a subject, the methods comprisingadministering to the subject an effective amount of an antibody orfragment thereof of the invention that binds PD-1 and blocks PD-1binding to PD-L1. In one embodiment, the invention provides a method tostimulate or enhance T-cell stimulation in a subject. In one embodiment,the invention provides methods to inhibit a T-regulatory (Treg) cell ina subject, the methods comprising administering a therapeuticallyeffective amount of a blocking antibody or antigen-binding fragmentthereof of the invention to the subject in need thereof. In certainembodiments, the subject in need thereof may suffer from a disease ordisorder such as cancer or viral infection. In alternate embodiments,the invention provides for methods to inhibit or suppress T-cellactivation in a subject, the methods comprising administering atherapeutically effective amount of an activating antibody or fragmentthereof of the invention to the subject in need thereof. In oneembodiment, the subject may suffer from an autoimmune disease ordisorder.

In a sixth aspect, the invention provides therapeutic methods fortreating a disease or disorder such as cancer, autoimmune disease orviral infection in a subject using an anti-PD-1 antibody orantigen-binding portion of an antibody of the invention, wherein thetherapeutic methods comprise administering a therapeutically effectiveamount of a pharmaceutical composition comprising an antibody orfragment of an antibody of the invention to the subject in need thereof.The disorder treated is any disease or condition which is improved,ameliorated, inhibited or prevented by stimulation or inhibition of PD-1activity or signaling. In certain embodiments, the antibody orantigen-binding fragment thereof the invention is administered incombination with a second therapeutic agent to the subject in needthereof. The second therapeutic agent may be selected from the groupconsisting of an antibody to another T-cell co-inhibitor, an antibody toa tumor cell antigen, an antibody to a T-cell receptor, an antibody to aFc receptor, an antibody to an epitope on a virally infected cell, anantibody to an autoimmune tissue antigen, an antibody to PD-L1, acytotoxic agent, an anti-cancer drug, an anti-viral drug, ananti-inflammatory drug (e.g., corticosteroids), chemotherapeutic agent,radiation therapy, an immunosuppressant and any other drug or therapyknown in the art. In certain embodiments, the second therapeutic agentmay be an agent that helps to counteract or reduce any possible sideeffect(s) associated with an antibody or antigen-binding fragmentthereof of the invention, if such side effect(s) should occur.

In certain embodiments, the present invention provides methods forsuppressing tumor growth. In certain embodiments, the present inventionprovides methods to enhance survival of cancer patients. Examples ofcancer include, but are not limited to, primary and/or recurrent cancer,including brain cancer (e.g., glioblastoma multiforme), lung cancer(e.g., non-small cell lung cancer), squamous cell carcinoma of head andneck, renal cell carcinoma, melanoma, multiple myeloma, prostate cancer,and colon cancer. The methods comprise administering a pharmaceuticalcomposition comprising a therapeutically effective amount of ananti-PD-1 antibody of the present invention in combination with a secondtherapeutic agent selected from the group consisting of a vascularendothelial growth factor (VEGF) antagonist (e.g., aflibercept,bevacizumab), an angiopoietin-2 (Ang2) inhibitor (e.g., an anti-Ang2antibody such as nesvacumab), a lymphocyte activation gene 3 (LAG-3)inhibitor, a cytotoxic T-lymphocyte antigen 4 (CTLA-4) inhibitor (e.g.,ipilimumab), a chemotherapeutic agent, and radiation therapy. Additionalexamples of additional therapies/therapeutic agents that can be used incombination with an anti-PD-1 antibody of the invention for use intreating cancer are described elsewhere herein.

The antibody or fragment thereof may be administered subcutaneously,intravenously, intradermally, intraperitoneally, orally,intramuscularly, or intracranially. The antibody or fragment thereof maybe administered at a dose of about 0.1 mg/kg of body weight to about 100mg/kg of body weight of the subject.

The present invention also includes use of an anti-PD-1 antibody orantigen-binding fragment thereof of the invention in the manufacture ofa medicament for the treatment of a disease or disorder that wouldbenefit from the blockade or enhancement of PD-1 binding and/orsignaling.

Other embodiments will become apparent from a review of the ensuingdetailed description.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic of the luciferase-based PD-1 bioassay described inExample 8 herein. Panel A: Inactive Jurkat cells; Panel B: Jurkat cellsare activated by T-cell receptor (TCR) clustering through the CD3×CD20bispecific antibody; Panel C: PD-1 activation attenuates response inactivated Jurkat cells; Panel D: Blocking PD-1 rescues the response inactivated Jurkat cells.

FIG. 2 illustrates tumor growth and survival results for mice implantedwith Colon-26 tumor cells at Day 0 and treated with the indicatedcombinations of molecules by injection at Days 3, 6, 10, 13 and 19(“early-treatment tumor model”). The graph depicts tumor volume (in mm³)for the different experimental groups at various time points afterimplantation. Upward arrows along the X-axis indicate the timing oftreatment injections. “mIgG2a” is IgG2 isotype control; “Fc” is human Fccontrol; “VEGF Trap” is aflibercept; “anti-PD-1” is anti-mouse PD-1clone RPMI-14; “anti-PD-L1” is an anti-PD-L1 monoclonal antibody asdescribed elsewhere herein.

FIG. 3 illustrates tumor growth and survival results for mice implantedwith Colon-26 tumor cells at Day 0 and treated with the indicatedcombinations of molecules by injection at Days 3, 6, 10, 13 and 19(“early-treatment tumor model”). The graph shows the tumor volume (inmm³) of individual mice in each experimental group at Day 28 afterimplantation. “mIgG2a” is IgG2 isotype control; “Fc” is human Fccontrol; “VEGF Trap” is aflibercept; “anti-PD-1” is anti-mouse PD-1clone RPMI-14; “anti-PD-L1” is an anti-PD-L1 monoclonal antibody asdescribed elsewhere herein.

DETAILED DESCRIPTION

Before the present methods are described, it is to be understood thatthis invention is not limited to particular methods, and experimentalconditions described, as such methods and conditions may vary. It isalso to be understood that the terminology used herein is for thepurpose of describing particular embodiments only, and is not intendedto be limiting, since the scope of the present invention will be limitedonly by the appended claims.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although any methods andmaterials similar or equivalent to those described herein can be used inthe practice or testing of the present invention, preferred methods andmaterials are now described. All publications mentioned herein areincorporated herein by reference in their entirety.

The term “PD-1” refers to the programmed death-1 protein, a T-cellco-inhibitor, also known as CD279. The amino acid sequence offull-length PD-1 is provided in GenBank as accession number NP 005009.2and is also referred to herein as SEQ ID NO: 327. The term “PD-1” alsoincludes protein variants of PD-1 having the amino acid sequence of SEQID NOs: 321, 322, 323, or 324. The term “PD-1” includes recombinant PD-1or a fragment thereof. The term also encompasses PD-1 or a fragmentthereof coupled to, for example, histidine tag, mouse or human Fc, or asignal sequence such as ROR1. For example, the term includes sequencesexemplified by SEQ ID NOs: 323 or 324, comprising a mouse Fc (mIgG2a) orhuman Fc (h IgG1) at the C-terminal, coupled to amino acid residues25-170 of full-length PD-1 with a C93S change. Protein variants asexemplified by SEQ ID NO: 321 comprise a histidine tag at theC-terminal, coupled to amino acid residues 25-170 of full length PD-1.Unless specified as being from a non-human species, the term “PD-1”means human PD-1.

PD-1 is a member of the CD28/CTLA-4/ICOS family of T-cell co-inhibitors.PD-1 is a 288-amino acid protein with an extracellular N-terminal domainwhich is IgV-like, a transmembrane domain and an intracellular domaincontaining an immunoreceptor tyrosine-based inhibitory (ITIM) motif andan immunoreceptor tyrosine-based switch (ITSM) motif (Chattopadhyay etal 2009, Immunol. Rev.). The PD-1 receptor has two ligands, PD-ligand-1(PD-L1) and PD-L2.

The term “PD-L1” refers to the ligand of the PD-1 receptor also known asCD274 and B7H1. The amino acid sequence of full-length PD-L1 is providedin GenBank as accession number NP 054862.1 and is also referred toherein as SEQ ID NO: 328. The term also encompasses PD-L1 or a fragmentthereof coupled to, for example, histidine tag, mouse or human Fc, or asignal sequence such as ROR1. For example, the term includes sequencesexemplified by SEQ ID NOs: 325 or 326, comprising a mouse Fc (mIgG2a) orhuman Fc (h IgG1) at the C-terminal, coupled to amino acid residues19-239 of full-length PD-L1. PD-L1 is a 290 amino acid protein with anextracellular IgV-like domain, a transmembrane domain and a highlyconserved intracellular domain of approximately 30 amino acids. PD-L1 isconstitutively expressed on many cells such as antigen presenting cells(e.g., dendritic cells, macrophages, and B-cells) and on hematopoieticand non-hematopoietic cells (e.g., vascular endothelial cells,pancreatic islets, and sites of immune privilege). PD-L1 is alsoexpressed on a wide variety of tumors, virally-infected cells andautoimmune tissue, and is a component of the immunosuppressive milieu(Ribas 2012, NEJM 366: 2517-2519).

As used herein, the term “T-cell co-inhibitor” refers to a ligand and/orreceptor which modulates the immune response via T-cell activation orsuppression. The term “T-cell co-inhibitor”, also known as T-cellco-signaling molecule, includes, but is not limited to, lymphocyteactivation gene 3 protein (LAG-3, also known as CD223), cytotoxicT-lymphocyte antigen-4 (CTLA-4), B and T lymphocyte attenuator (BILA),CD-28, 2B4, LY108, T-cell immunoglobulin and mucin 3(TIM3), T-cellimmunoreceptor with immunoglobulin and ITIM (TIGIT; also known asVSIG9), leucocyte associated immunoglobulin-like receptor 1 (LAIR1; alsoknown as CD305), inducible T-cell costimulator (ICOS; also known asCD278), V-domain Ig suppressor of T-cell activation (VISTA) and CD160.

As used herein, the term “Fc receptor” refers to the surface receptorprotein found on immune cells including B lymphocytes, natural killercells, macrophages, basophils, neutrophils, and mast cells, which has abinding specificity for the Fc region of an antibody. The term “Fcreceptor” includes, but is not limited to, a Fcγ receptor [e.g., FcγRI(CD64), FcγRIIA (CD32), FcγRIIB (CD32), FcγRIIIA (CD16a), and FcγRIIIB(CD16b)], Fcα receptor (e.g., FcαRI or CD89) and Fcε receptor [e.g.,FcεRI, and FcεRII (CD23)].

The term “antibody”, as used herein, is intended to refer toimmunoglobulin molecules comprised of four polypeptide chains, two heavy(H) chains and two light (L) chains inter-connected by disulfide bonds(i.e., “full antibody molecules”), as well as multimers thereof (e.g.IgM) or antigen-binding fragments thereof. Each heavy chain is comprisedof a heavy chain variable region (“HCVR” or “V_(H)”) and a heavy chainconstant region (comprised of domains C_(H)1, C_(H)2 and C_(H)3). Eachlight chain is comprised of a light chain variable region (“LCVR or“V_(L)”) and a light chain constant region (CO. The V_(H) and V_(L)regions can be further subdivided into regions of hypervariability,termed complementarity determining regions (CDR), interspersed withregions that are more conserved, termed framework regions (FR). EachV_(H) and V_(L) is composed of three CDRs and four FRs, arranged fromamino-terminus to carboxy-terminus in the following order: FR1, CDR1,FR2, CDR2, FR3, CDR3, FR4. In certain embodiments of the invention, theFRs of the antibody (or antigen binding fragment thereof) may beidentical to the human germline sequences, or may be naturally orartificially modified. An amino acid consensus sequence may be definedbased on a side-by-side analysis of two or more CDRs.

Substitution of one or more CDR residues or omission of one or more CDRsis also possible. Antibodies have been described in the scientificliterature in which one or two CDRs can be dispensed with for binding.Padlan et al. (1995 FASEB J. 9:133-139) analyzed the contact regionsbetween antibodies and their antigens, based on published crystalstructures, and concluded that only about one fifth to one third of CDRresidues actually contact the antigen. Padlan also found many antibodiesin which one or two CDRs had no amino acids in contact with an antigen(see also, Vajdos et al. 2002 J Mol Biol 320:415-428).

CDR residues not contacting antigen can be identified based on previousstudies (for example residues H60-H65 in CDRH2 are often not required),from regions of Kabat CDRs lying outside Chothia CDRs, by molecularmodeling and/or empirically. If a CDR or residue(s) thereof is omitted,it is usually substituted with an amino acid occupying the correspondingposition in another human antibody sequence or a consensus of suchsequences. Positions for substitution within CDRs and amino acids tosubstitute can also be selected empirically. Empirical substitutions canbe conservative or non-conservative substitutions.

The fully human anti-PD-1 monoclonal antibodies disclosed herein maycomprise one or more amino acid substitutions, insertions and/ordeletions in the framework and/or CDR regions of the heavy and lightchain variable domains as compared to the corresponding germlinesequences. Such mutations can be readily ascertained by comparing theamino acid sequences disclosed herein to germline sequences availablefrom, for example, public antibody sequence databases. The presentinvention includes antibodies, and antigen-binding fragments thereof,which are derived from any of the amino acid sequences disclosed herein,wherein one or more amino acids within one or more framework and/or CDRregions are mutated to the corresponding residue(s) of the germlinesequence from which the antibody was derived, or to the correspondingresidue(s) of another human germline sequence, or to a conservativeamino acid substitution of the corresponding germline residue(s) (suchsequence changes are referred to herein collectively as “germlinemutations”). A person of ordinary skill in the art, starting with theheavy and light chain variable region sequences disclosed herein, caneasily produce numerous antibodies and antigen-binding fragments whichcomprise one or more individual germline mutations or combinationsthereof. In certain embodiments, all of the framework and/or CDRresidues within the V_(H) and/or V_(L) domains are mutated back to theresidues found in the original germline sequence from which the antibodywas derived. In other embodiments, only certain residues are mutatedback to the original germline sequence, e.g., only the mutated residuesfound within the first 8 amino acids of FR1 or within the last 8 aminoacids of FR4, or only the mutated residues found within CDR1, CDR2 orCDR3. In other embodiments, one or more of the framework and/or CDRresidue(s) are mutated to the corresponding residue(s) of a differentgermline sequence (i.e., a germline sequence that is different from thegermline sequence from which the antibody was originally derived).Furthermore, the antibodies of the present invention may contain anycombination of two or more germline mutations within the frameworkand/or CDR regions, e.g., wherein certain individual residues aremutated to the corresponding residue of a particular germline sequencewhile certain other residues that differ from the original germlinesequence are maintained or are mutated to the corresponding residue of adifferent germline sequence. Once obtained, antibodies andantigen-binding fragments that contain one or more germline mutationscan be easily tested for one or more desired property such as, improvedbinding specificity, increased binding affinity, improved or enhancedantagonistic or agonistic biological properties (as the case may be),reduced immunogenicity, etc. Antibodies and antigen-binding fragmentsobtained in this general manner are encompassed within the presentinvention.

The present invention also includes fully human anti-PD-1 monoclonalantibodies comprising variants of any of the HCVR, LCVR, and/or CDRamino acid sequences disclosed herein having one or more conservativesubstitutions. For example, the present invention includes anti-PD-1antibodies having HCVR, LCVR, and/or CDR amino acid sequences with,e.g., 10 or fewer, 8 or fewer, 6 or fewer, 4 or fewer, etc. conservativeamino acid substitutions relative to any of the HCVR, LCVR, and/or CDRamino acid sequences disclosed herein.

The term “human antibody”, as used herein, is intended to includeantibodies having variable and constant regions derived from humangermline immunoglobulin sequences. The human mAbs of the invention mayinclude amino acid residues not encoded by human germline immunoglobulinsequences (e.g., mutations introduced by random or site-specificmutagenesis in vitro or by somatic mutation in vivo), for example in theCDRs and in particular CDR3. However, the term “human antibody”, as usedherein, is not intended to include mAbs in which CDR sequences derivedfrom the germline of another mammalian species (e.g., mouse), have beengrafted onto human FR sequences. The term includes antibodiesrecombinantly produced in a non-human mammal, or in cells of a non-humanmammal. The term is not intended to include antibodies isolated from orgenerated in a human subject.

The term “recombinant”, as used herein, refers to antibodies orantigen-binding fragments thereof of the invention created, expressed,isolated or obtained by technologies or methods known in the art asrecombinant DNA technology which include, e.g., DNA splicing andtransgenic expression. The term refers to antibodies expressed in anon-human mammal (including transgenic non-human mammals, e.g.,transgenic mice), or a cell (e.g., CHO cells) expression system orisolated from a recombinant combinatorial human antibody library.

The term “multi-specific antigen-binding molecules”, as used hereinrefers to bispecific, tri-specific or multi-specific antigen-bindingmolecules, and antigen-binding fragments thereof. Multi-specificantigen-binding molecules may be specific for different epitopes of onetarget polypeptide or may contain antigen-binding domains specific forepitopes of more than one target polypeptide. A multi-specificantigen-binding molecule can be a single multifunctional polypeptide, orit can be a multimeric complex of two or more polypeptides that arecovalently or non-covalently associated with one another. The term“multi-specific antigen-binding molecules” includes antibodies of thepresent invention that may be linked to or co-expressed with anotherfunctional molecule, e.g., another peptide or protein. For example, anantibody or fragment thereof can be functionally linked (e.g., bychemical coupling, genetic fusion, non-covalent association orotherwise) to one or more other molecular entities, such as a protein orfragment thereof to produce a bi-specific or a multi-specificantigen-binding molecule with a second binding specificity. According tothe present invention, the term “multi-specific antigen-bindingmolecules” also includes bi-specific, tri-specific or multi-specificantibodies or antigen-binding fragments thereof. In certain embodiments,an antibody of the present invention is functionally linked to anotherantibody or antigen-binding fragment thereof to produce a bispecificantibody with a second binding specificity. Bispecific andmulti-specific antibodies of the present invention are describedelsewhere herein.

The term “specifically binds,” or “binds specifically to”, or the like,means that an antibody or antigen-binding fragment thereof forms acomplex with an antigen that is relatively stable under physiologicconditions. Specific binding can be characterized by an equilibriumdissociation constant of at least about 1×10⁻⁸ M or less (e.g., asmaller K_(D) denotes a tighter binding). Methods for determiningwhether two molecules specifically bind are well known in the art andinclude, for example, equilibrium dialysis, surface plasmon resonance,and the like. As described herein, antibodies have been identified bysurface plasmon resonance, e.g., BIACORE™, which bind specifically toPD-1. Moreover, multi-specific antibodies that bind to one domain inPD-1 and one or more additional antigens or a bi-specific that binds totwo different regions of PD-1 are nonetheless considered antibodies that“specifically bind”, as used herein.

The term “high affinity” antibody refers to those mAbs having a bindingaffinity to PD-1, expressed as K_(D), of at least 10⁻⁷ M; preferably10⁻⁸M; more preferably 10⁻⁸M, even more preferably 10⁻¹⁰ M, even morepreferably 10⁻¹¹ M, as measured by surface plasmon resonance, e.g.,BIACORE™ or solution-affinity ELISA.

By the term “slow off rate”, “Koff” or “kd” is meant an antibody thatdissociates from PD-1, with a rate constant of 1×10⁻³ s⁻¹ or less,preferably 1×10⁻⁴ s⁻¹ or less, as determined by surface plasmonresonance, e.g., BIACORE™′

The terms “antigen-binding portion” of an antibody, “antigen-bindingfragment” of an antibody, and the like, as used herein, include anynaturally occurring, enzymatically obtainable, synthetic, or geneticallyengineered polypeptide or glycoprotein that specifically binds anantigen to form a complex. The terms “antigen-binding fragment” of anantibody, or “antibody fragment”, as used herein, refers to one or morefragments of an antibody that retain the ability to bind to PD-1.

In specific embodiments, antibody or antibody fragments of the inventionmay be conjugated to a moiety such a ligand or a therapeutic moiety(“immunoconjugate”), such as an antibiotic, a second anti-PD-1 antibody,or an antibody to another antigen such a tumor-specific antigen, anautoimmune tissue antigen, a virally-infected cell antigen, a Fcreceptor, a T-cell receptor, or a T-cell co-inhibitor, or animmunotoxin, or any other therapeutic moiety useful for treating adisease or condition including cancer, autoimmune disease or chronicviral infection.

An “isolated antibody”, as used herein, is intended to refer to anantibody that is substantially free of other antibodies (Abs) havingdifferent antigenic specificities (e.g., an isolated antibody thatspecifically binds PD-1, or a fragment thereof, is substantially free ofAbs that specifically bind antigens other than PD-1.

A “blocking antibody” or a “neutralizing antibody”, as used herein (oran “antibody that neutralizes PD-1 activity” or “antagonist antibody”),is intended to refer to an antibody whose binding to PD-1 results ininhibition of at least one biological activity of PD-1. For example, anantibody of the invention may prevent or block PD-1 binding to PD-L1.

An “activating antibody” or an “enhancing antibody”, as used herein (oran “agonist antibody”), is intended to refer to an antibody whosebinding to PD-1 results in increasing or stimulating at least onebiological activity of PD-1. For example, an antibody of the inventionmay increase PD-1 binding to PD-L1.

The term “surface plasmon resonance”, as used herein, refers to anoptical phenomenon that allows for the analysis of real-timebiomolecular interactions by detection of alterations in proteinconcentrations within a biosensor matrix, for example using the BIACORE™system (Pharmacia Biosensor AB, Uppsala, Sweden and Piscataway, N.J.).

The term “K_(D)”, as used herein, is intended to refer to theequilibrium dissociation constant of a particular antibody-antigeninteraction.

The term “epitope” refers to an antigenic determinant that interactswith a specific antigen binding site in the variable region of anantibody molecule known as a paratope. A single antigen may have morethan one epitope. Thus, different antibodies may bind to different areason an antigen and may have different biological effects. The term“epitope” also refers to a site on an antigen to which B and/or T cellsrespond. It also refers to a region of an antigen that is bound by anantibody. Epitopes may be defined as structural or functional.Functional epitopes are generally a subset of the structural epitopesand have those residues that directly contribute to the affinity of theinteraction. Epitopes may also be conformational, that is, composed ofnon-linear amino acids. In certain embodiments, epitopes may includedeterminants that are chemically active surface groupings of moleculessuch as amino acids, sugar side chains, phosphoryl groups, or sulfonylgroups, and, in certain embodiments, may have specific three-dimensionalstructural characteristics, and/or specific charge characteristics.

The term “substantial identity” or “substantially identical,” whenreferring to a nucleic acid or fragment thereof, indicates that, whenoptimally aligned with appropriate nucleotide insertions or deletionswith another nucleic acid (or its complementary strand), there isnucleotide sequence identity in at least about 90%, and more preferablyat least about 95%, 96%, 97%, 98% or 99% of the nucleotide bases, asmeasured by any well-known algorithm of sequence identity, such asFASTA, BLAST or GAP, as discussed below. A nucleic acid molecule havingsubstantial identity to a reference nucleic acid molecule may, incertain instances, encode a polypeptide having the same or substantiallysimilar amino acid sequence as the polypeptide encoded by the referencenucleic acid molecule.

As applied to polypeptides, the term “substantial similarity” or“substantially similar” means that two peptide sequences, when optimallyaligned, such as by the programs GAP or BESTFIT using default gapweights, share at least 90% sequence identity, even more preferably atleast 95%, 98% or 99% sequence identity. Preferably, residue positions,which are not identical, differ by conservative amino acidsubstitutions. A “conservative amino acid substitution” is one in whichan amino acid residue is substituted by another amino acid residuehaving a side chain (R group) with similar chemical properties (e.g.,charge or hydrophobicity). In general, a conservative amino acidsubstitution will not substantially change the functional properties ofa protein. In cases where two or more amino acid sequences differ fromeach other by conservative substitutions, the percent or degree ofsimilarity may be adjusted upwards to correct for the conservativenature of the substitution. Means for making this adjustment are wellknown to those of skill in the art. See, e.g., Pearson (1994) MethodsMol. Biol. 24: 307-331, which is herein incorporated by reference.Examples of groups of amino acids that have side chains with similarchemical properties include 1) aliphatic side chains: glycine, alanine,valine, leucine and isoleucine; 2) aliphatic-hydroxyl side chains:serine and threonine; 3) amide-containing side chains: asparagine andglutamine; 4) aromatic side chains: phenylalanine, tyrosine, andtryptophan; 5) basic side chains: lysine, arginine, and histidine; 6)acidic side chains: aspartate and glutamate, and 7) sulfur-containingside chains: cysteine and methionine. Preferred conservative amino acidssubstitution groups are: valine-leucine-isoleucine,phenylalanine-tyrosine, lysine-arginine, alanine-valine,glutamate-aspartate, and asparagine-glutamine. Alternatively, aconservative replacement is any change having a positive value in thePAM250 log-likelihood matrix disclosed in Gonnet et al. (1992) Science256: 1443 45, herein incorporated by reference. A “moderatelyconservative” replacement is any change having a nonnegative value inthe PAM250 log-likelihood matrix.

Sequence similarity for polypeptides is typically measured usingsequence analysis software. Protein analysis software matches similarsequences using measures of similarity assigned to varioussubstitutions, deletions and other modifications, including conservativeamino acid substitutions. For instance, GCG software contains programssuch as GAP and BESTFIT which can be used with default parameters todetermine sequence homology or sequence identity between closely relatedpolypeptides, such as homologous polypeptides from different species oforganisms or between a wild type protein and a mutein thereof. See,e.g., GCG Version 6.1. Polypeptide sequences also can be compared usingFASTA with default or recommended parameters; a program in GCG Version6.1. FASTA (e.g., FASTA2 and FASTA3) provides alignments and percentsequence identity of the regions of the best overlap between the queryand search sequences (Pearson (2000) supra). Another preferred algorithmwhen comparing a sequence of the invention to a database containing alarge number of sequences from different organisms is the computerprogram BLAST, especially BLASTP or TBLASTN, using default parameters.See, e.g., Altschul et al. (1990) J. Mol. Biol. 215: 403-410 and (1997)Nucleic Acids Res. 25:3389-3402, each of which is herein incorporated byreference.

By the phrase “therapeutically effective amount” is meant an amount thatproduces the desired effect for which it is administered. The exactamount will depend on the purpose of the treatment, and will beascertainable by one skilled in the art using known techniques (see, forexample, Lloyd (1999) The Art, Science and Technology of PharmaceuticalCompounding).

As used herein, the term “subject” refers to an animal, preferably amammal, in need of amelioration, prevention and/or treatment of adisease or disorder such as chronic viral infection, cancer orautoimmune disease.

As used herein, “anti-cancer drug” means any agent useful to treatcancer including, but not limited to, cytotoxins and agents such asantimetabolites, alkylating agents, anthracyclines, antibiotics,antimitotic agents, procarbazine, hydroxyurea, asparaginase,corticosteroids, mytotane (O,P′-(DDD)), biologics (e.g., antibodies andinterferons) and radioactive agents. As used herein, “a cytotoxin orcytotoxic agent”, also refers to a chemotherapeutic agent and means anyagent that is detrimental to cells. Examples include Taxol®(paclitaxel), temozolamide, cytochalasin B, gramicidin D, ethidiumbromide, emetine, cisplatin, mitomycin, etoposide, tenoposide,vincristine, vinbiastine, coichicin, doxorubicin, daunorubicin,dihydroxy anthracin dione, mitoxantrone, mithramycin, actinomycin D,1-dehydrotestosterone, glucocorticoids, procaine, tetracaine, lidocaine,propranolol, and puromycin and analogs or homologs thereof.

As used herein, the term “anti-viral drug” refers to any drug or therapyused to treat, prevent, or ameliorate a viral infection in a hostsubject. The term “anti-viral drug” includes, but is not limited tozidovudine, lamivudine, abacavir, ribavirin, lopinavir, efavirenz,cobicistat, tenofovir, rilpivirine, analgesics and corticosteroids. Inthe context of the present invention, the viral infections includelong-term or chronic infections caused by viruses including, but notlimited to, human immunodeficiency virus (HIV), hepatitis B virus (HBV),hepatitis C virus (HCV), human papilloma virus (HPV), lymphocyticchoriomeningitis virus (LCMV), and simian immunodeficiency virus (SIV).

The antibodies and antigen-binding fragments of the present inventionspecifically bind to PD-1 and modulate the interaction of PD-1 withPD-L1. The anti-PD-1 antibodies may bind to PD-1 with high affinity orwith low affinity. In certain embodiments, the antibodies of the presentinvention may be blocking antibodies wherein the antibodies may bind toPD-1 and block the interaction of PD-1 with PD-L1. In some embodiments,the blocking antibodies of the invention may block the binding of PD-1to PD-L1 and/or stimulate or enhance T-cell activation. In someembodiments, the blocking antibodies may be useful for stimulating orenhancing the immune response and/or for treating a subject sufferingfrom cancer, or a chronic viral infection. The antibodies whenadministered to a subject in need thereof may reduce the chronicinfection by a virus such as HIV, LCMV or HBV in the subject. They maybe used to inhibit the growth of tumor cells in a subject. They may beused alone or as adjunct therapy with other therapeutic moieties ormodalities known in the art for treating cancer, or viral infection.

In other embodiments, the antibodies of the present invention may beactivating antibodies, wherein the antibodies may bind to PD-1 andenhance the interaction of PD-1 and PD-L1. In some embodiments, theactivating antibodies may enhance binding of PD-1 to PD-L1 and/orinhibit or suppress T-cell activation. The activating antibodies of thepresent invention may be useful for inhibiting the immune response in asubject and/or for treating autoimmune disease.

In certain embodiments, the anti-PD-1 antibodies may be multi-specificantigen-binding molecules, wherein they comprise a first bindingspecificity to PD-1 and a second binding specificity to an antigenselected from the group consisting of another T-cell co-inhibitor, anautoimmune tissue antigen, T-cell receptor, Fc receptor, T-cellreceptor, PD-L1, and a different epitope of PD-1.

In certain embodiments, the antibodies of the invention are obtainedfrom mice immunized with a primary immunogen, such as a full length PD-1[See GenBank accession number NP_005009.2 (SEQ ID NO: 327)] or with arecombinant form of PD-1 or modified human PD-1 fragments (SEQ ID NOs:321, 323, or 324) or with modified cynomolgus PD-1 fragments (SEQ ID NO:322), followed by immunization with a secondary immunogen, or with animmunogenically active fragment of PD-1.

The immunogen may be a biologically active and/or immunogenic fragmentof PD-1 or DNA encoding the active fragment thereof. The fragment may bederived from the N-terminal or C-terminal domain of PD-1. In certainembodiments of the invention, the immunogen is a fragment of PD-1 thatranges from amino acid residues 25-170 of SEQ ID NO: 327 with a C93Schange.

The peptides may be modified to include addition or substitution ofcertain residues for tagging or for purposes of conjugation to carriermolecules, such as, KLH. For example, a cysteine may be added at eitherthe N terminal or C terminal end of a peptide, or a linker sequence maybe added to prepare the peptide for conjugation to, for example, KLH forimmunization.

The full-length amino acid sequence of full length human PD-1 is shownas SEQ ID NO: 327.

In certain embodiments, antibodies that bind specifically to PD-1 may beprepared using fragments of the above-noted regions, or peptides thatextend beyond the designated regions by about 5 to about 20 amino acidresidues from either, or both, the N or C terminal ends of the regionsdescribed herein. In certain embodiments, any combination of theabove-noted regions or fragments thereof may be used in the preparationof PD-1 specific antibodies. In certain embodiments, any one or more ofthe above-noted regions of PD-1, or fragments thereof may be used forpreparing monospecific, bispecific, or multispecific antibodies.

Certain anti-PD-1 antibodies of the present invention are able to bindto and neutralize the activity of PD-1, as determined by in vitro or invivo assays. The ability of the antibodies of the invention to bind toand neutralize the activity of PD-1 may be measured using any standardmethod known to those skilled in the art, including binding assays, oractivity assays, as described herein.

Non-limiting, exemplary in vitro assays for measuring binding activityare illustrated in Examples herein. In Example 3, the binding affinitiesand kinetic constants of human anti-PD-1 antibodies for human PD-1 andcynomolgus PD-1 were determined by surface plasmon resonance and themeasurements were conducted on a Biacore 4000 or T200 instrument. InExamples 4 and 5, blocking assays were used to determine the ability ofthe anti-PD-1 antibodies to block PD-L1-binding ability of PD-1 invitro. In Example 6, blocking assays were used to determinecross-competition between anti-PD-1 antibodies. Example 7 describes thebinding of the antibodies to cells overexpressing PD-1. In Example 8, aluciferase assay was used to determine the ability of anti-PD-1antibodies to antagonize PD-1/PD-L1 signaling in T-cells.

In certain embodiments, the antibodies of the present invention are ableto enhance or stimulate T-cell activation in vitro and in a subject withcancer or in a subject infected with a virus such as LCMV. In certainembodiments, the antibodies of the present invention are used incombination with a second therapeutic agent, such as an antibody to asecond T-cell co-inhibitor, to enhance the immune response and inhibittumor growth in a subject.

The antibodies specific for PD-1 may contain no additional labels ormoieties, or they may contain an N-terminal or C-terminal label ormoiety. In one embodiment, the label or moiety is biotin. In a bindingassay, the location of a label (if any) may determine the orientation ofthe peptide relative to the surface upon which the peptide is bound. Forexample, if a surface is coated with avidin, a peptide containing anN-terminal biotin will be oriented such that the C-terminal portion ofthe peptide will be distal to the surface. In one embodiment, the labelmay be a radionuclide, a fluorescent dye or a MRI-detectable label. Incertain embodiments, such labeled antibodies may be used in diagnosticassays including imaging assays.

Antigen-Binding Fragments of Antibodies

Unless specifically indicated otherwise, the term “antibody,” as usedherein, shall be understood to encompass antibody molecules comprisingtwo immunoglobulin heavy chains and two immunoglobulin light chains(i.e., “full antibody molecules”) as well as antigen-binding fragmentsthereof. The terms “antigen-binding portion” of an antibody,“antigen-binding fragment” of an antibody, and the like, as used herein,include any naturally occurring, enzymatically obtainable, synthetic, orgenetically engineered polypeptide or glycoprotein that specificallybinds an antigen to form a complex. The terms “antigen-binding fragment”of an antibody, or “antibody fragment”, as used herein, refers to one ormore fragments of an antibody that retain the ability to specificallybind to PD-1. An antibody fragment may include a Fab fragment, a F(ab′)₂fragment, a Fv fragment, a dAb fragment, a fragment containing a CDR, oran isolated CDR. In certain embodiments, the term “antigen-bindingfragment” refers to a polypeptide fragment of a multi-specificantigen-binding molecule. In such embodiments, the term” antigen-bindingfragment” includes, e.g., an extracellular domain of PD-L1 which bindsspecifically to PD-1. Antigen-binding fragments of an antibody may bederived, e.g., from full antibody molecules using any suitable standardtechniques such as proteolytic digestion or recombinant geneticengineering techniques involving the manipulation and expression of DNAencoding antibody variable and (optionally) constant domains. Such DNAis known and/or is readily available from, e.g., commercial sources, DNAlibraries (including, e.g., phage-antibody libraries), or can besynthesized. The DNA may be sequenced and manipulated chemically or byusing molecular biology techniques, for example, to arrange one or morevariable and/or constant domains into a suitable configuration, or tointroduce codons, create cysteine residues, modify, add or delete aminoacids, etc.

Non-limiting examples of antigen-binding fragments include: (i) Fabfragments; (ii) F(ab′)2 fragments; (iii) Fd fragments; (iv) Fvfragments; (v) single-chain Fv (scFv) molecules; (vi) dAb fragments; and(vii) minimal recognition units consisting of the amino acid residuesthat mimic the hypervariable region of an antibody (e.g., an isolatedcomplementarity determining region (CDR) such as a CDR3 peptide), or aconstrained FR3-CDR3-FR4 peptide. Other engineered molecules, such asdomain-specific antibodies, single domain antibodies, domain-deletedantibodies, chimeric antibodies, CDR-grafted antibodies, diabodies,triabodies, tetrabodies, minibodies, nanobodies (e.g. monovalentnanobodies, bivalent nanobodies, etc.), small modularimmunopharmaceuticals (SMIPs), and shark variable IgNAR domains, arealso encompassed within the expression “antigen-binding fragment,” asused herein.

An antigen-binding fragment of an antibody will typically comprise atleast one variable domain. The variable domain may be of any size oramino acid composition and will generally comprise at least one CDR,which is adjacent to or in frame with one or more framework sequences.In antigen-binding fragments having a V_(H) domain associated with aV_(L) domain, the V_(H) and V_(L) domains may be situated relative toone another in any suitable arrangement. For example, the variableregion may be dimeric and contain V_(H)-V_(H), V_(H)-V_(L) orV_(L)-V_(L) dimers. Alternatively, the antigen-binding fragment of anantibody may contain a monomeric V_(H) or V_(L) domain.

In certain embodiments, an antigen-binding fragment of an antibody maycontain at least one variable domain covalently linked to at least oneconstant domain. Non-limiting, exemplary configurations of variable andconstant domains that may be found within an antigen-binding fragment ofan antibody of the present invention include: (i) V_(H)-C_(H)1; (ii)V_(H)-C_(H)2; (iii) V_(H)-C_(H)3; (iv) V_(H)-C_(H)1-C_(H)2; (V)V_(H)-C_(H)1-C_(H)2-C_(H)3; (vi) V_(H)-C_(H)2-C_(H)3; V_(H)-C_(L);V_(L)—C_(H)1; (ix) V_(L)-C_(H)2; (x) V_(L)-C_(H)3; (xi)V_(L)-C_(H)1-C_(H)2; (xii) V_(L)-C_(H)1-C_(H)2-C_(H)3; (xiii)V_(L)-C_(H)2-C_(H)3; and (xiv) V_(L)-C_(L). In any configuration ofvariable and constant domains, including any of the exemplaryconfigurations listed above, the variable and constant domains may beeither directly linked to one another or may be linked by a full orpartial hinge or linker region. A hinge region may consist of at least 2(e.g., 5, 10, 15, 20, 40, 60 or more) amino acids, which result in aflexible or semi-flexible linkage between adjacent variable and/orconstant domains in a single polypeptide molecule. Moreover, anantigen-binding fragment of an antibody of the present invention maycomprise a homo-dimer or hetero-dimer (or other multimer) of any of thevariable and constant domain configurations listed above in non-covalentassociation with one another and/or with one or more monomeric V_(H) orV_(L) domain (e.g., by disulfide bond(s)).

As with full antibody molecules, antigen-binding fragments may bemono-specific or multi-specific (e.g., bi-specific). A multi-specificantigen-binding fragment of an antibody will typically comprise at leasttwo different variable domains, wherein each variable domain is capableof specifically binding to a separate antigen or to a different epitopeon the same antigen. Any multi-specific antibody format, including theexemplary bi-specific antibody formats disclosed herein, may be adaptedfor use in the context of an antigen-binding fragment of an antibody ofthe present invention using routine techniques available in the art.

Preparation of Human Antibodies

Methods for generating human antibodies in transgenic mice are known inthe art. Any such known methods can be used in the context of thepresent invention to make human antibodies that specifically bind toPD-1.

An immunogen comprising any one of the following can be used to generateantibodies to PD-1. In certain embodiments, the antibodies of theinvention are obtained from mice immunized with a full length, nativePD-1 (See GenBank accession number NP_005009.2) (SEQ ID NO: 327), orwith a recombinant PD-1 peptide. Alternatively, PD-1 or a fragmentthereof may be produced using standard biochemical techniques andmodified (SEQ ID NOS: 321-324) and used as immunogen.

In certain embodiments, the immunogen may be a peptide from the Nterminal or C terminal end of PD-1. In one embodiment, the immunogen isthe extracellular domain or the IgV-like domain of PD-1. In certainembodiments of the invention, the immunogen is a fragment of PD-1 thatranges from about amino acid residues 25-170 of SEQ ID NO: 327 with aC93S change.

In some embodiments, the immunogen may be a recombinant PD-1 peptideexpressed in E. coli or in any other eukaryotic or mammalian cells suchas Chinese hamster ovary (CHO) cells.

In certain embodiments, antibodies that bind specifically to PD-1 may beprepared using fragments of the above-noted regions, or peptides thatextend beyond the designated regions by about 5 to about 20 amino acidresidues from either, or both, the N or C terminal ends of the regionsdescribed herein. In certain embodiments, any combination of theabove-noted regions or fragments thereof may be used in the preparationof PD-1 specific antibodies.

Using VELOCIMMUNE® technology (see, for example, U.S. Pat. No.6,596,541, Regeneron Pharmaceuticals, VELOCIMMUNE®) or any other knownmethod for generating monoclonal antibodies, high affinity chimericantibodies to PD-1 are initially isolated having a human variable regionand a mouse constant region. The VELOCIMMUNE® technology involvesgeneration of a transgenic mouse having a genome comprising human heavyand light chain variable regions operably linked to endogenous mouseconstant region loci such that the mouse produces an antibody comprisinga human variable region and a mouse constant region in response toantigenic stimulation. The DNA encoding the variable regions of theheavy and light chains of the antibody are isolated and operably linkedto DNA encoding the human heavy and light chain constant regions. TheDNA is then expressed in a cell capable of expressing the fully humanantibody.

Bioequivalents

The anti-PD-1 antibodies and antibody fragments of the present inventionencompass proteins having amino acid sequences that vary from those ofthe described antibodies, but that retain the ability to bind PD-1. Suchvariant antibodies and antibody fragments comprise one or moreadditions, deletions, or substitutions of amino acids when compared toparent sequence, but exhibit biological activity that is essentiallyequivalent to that of the described antibodies. Likewise, theantibody-encoding DNA sequences of the present invention encompasssequences that comprise one or more additions, deletions, orsubstitutions of nucleotides when compared to the disclosed sequence,but that encode an antibody or antibody fragment that is essentiallybioequivalent to an antibody or antibody fragment of the invention.

Two antigen-binding proteins, or antibodies, are consideredbioequivalent if, for example, they are pharmaceutical equivalents orpharmaceutical alternatives whose rate and extent of absorption do notshow a significant difference when administered at the same molar doseunder similar experimental conditions, either single dose or multipledoses. Some antibodies will be considered equivalents or pharmaceuticalalternatives if they are equivalent in the extent of their absorptionbut not in their rate of absorption and yet may be consideredbioequivalent because such differences in the rate of absorption areintentional and are reflected in the labeling, are not essential to theattainment of effective body drug concentrations on, e.g., chronic use,and are considered medically insignificant for the particular drugproduct studied.

In one embodiment, two antigen-binding proteins are bioequivalent ifthere are no clinically meaningful differences in their safety, purity,or potency.

In one embodiment, two antigen-binding proteins are bioequivalent if apatient can be switched one or more times between the reference productand the biological product without an expected increase in the risk ofadverse effects, including a clinically significant change inimmunogenicity, or diminished effectiveness, as compared to continuedtherapy without such switching.

In one embodiment, two antigen-binding proteins are bioequivalent ifthey both act by a common mechanism or mechanisms of action for thecondition or conditions of use, to the extent that such mechanisms areknown.

Bioequivalence may be demonstrated by in vivo and/or in vitro methods.Bioequivalence measures include, e.g., (a) an in vivo test in humans orother mammals, in which the concentration of the antibody or itsmetabolites is measured in blood, plasma, serum, or other biologicalfluid as a function of time; (b) an in vitro test that has beencorrelated with and is reasonably predictive of human in vivobioavailability data; (c) an in vivo test in humans or other mammals inwhich the appropriate acute pharmacological effect of the antibody (orits target) is measured as a function of time; and (d) in awell-controlled clinical trial that establishes safety, efficacy, orbioavailability or bioequivalence of an antibody.

Bioequivalent variants of the antibodies of the invention may beconstructed by, for example, making various substitutions of residues orsequences or deleting terminal or internal residues or sequences notneeded for biological activity. For example, cysteine residues notessential for biological activity can be deleted or replaced with otheramino acids to prevent formation of unnecessary or incorrectintramolecular disulfide bridges upon renaturation. In other contexts,bioequivalent antibodies may include antibody variants comprising aminoacid changes, which modify the glycosylation characteristics of theantibodies, e.g., mutations that eliminate or remove glycosylation.

Anti-PD-1 Antibodies Comprising Fc Variants

According to certain embodiments of the present invention, anti-PD-1antibodies are provided comprising an Fc domain comprising one or moremutations which enhance or diminish antibody binding to the FcRnreceptor, e.g., at acidic pH as compared to neutral pH. For example, thepresent invention includes anti-PD-1 antibodies comprising a mutation inthe C_(H)2 or a C_(H)3 region of the Fc domain, wherein the mutation(s)increases the affinity of the Fc domain to FcRn in an acidic environment(e.g., in an endosome where pH ranges from about 5.5 to about 6.0). Suchmutations may result in an increase in serum half-life of the antibodywhen administered to an animal. Non-limiting examples of such Fcmodifications include, e.g., a modification at position 250 (e.g., E orQ); 250 and 428 (e.g., L or F); 252 (e.g., L/Y/F/W or T), 254 (e.g., Sor T), and 256 (e.g., S/R/Q/E/D or T); or a modification at position 428and/or 433 (e.g., H/L/R/S/P/Q or K) and/or 434 (e.g., A, W, H, F or Y[N434A, N434W, N434H, N434F or N434Y]); or a modification at position250 and/or 428; or a modification at position 307 or 308 (e.g., 308F,V308F), and 434. In one embodiment, the modification comprises a 428L(e.g., M428L) and 434S (e.g., N434S) modification; a 428L, 2591 (e.g.,V2591), and 308F (e.g., V308F) modification; a 433K (e.g., H433K) and a434 (e.g., 434Y) modification; a 252, 254, and 256 (e.g., 252Y, 254T,and 256E) modification; a 250Q and 428L modification (e.g., T250Q andM428L); and a 307 and/or 308 modification (e.g., 308F or 308P). In yetanother embodiment, the modification comprises a 265A (e.g., D265A)and/or a 297A (e.g., N297A) modification.

For example, the present invention includes anti-PD-1 antibodiescomprising an Fc domain comprising one or more pairs or groups ofmutations selected from the group consisting of: 250Q and 248L (e.g.,T250Q and M248L); 252Y, 254T and 256E (e.g., M252Y, S254T and T256E);428L and 434S (e.g., M428L and N434S); 2571 and 3111 (e.g., P2571 and03111); 2571 and 434H (e.g., P2571 and N434H); 376V and 434H (e.g.,D376V and N434H); 307A, 380A and 434A (e.g., 1307A, E380A and N434A);and 433K and 434F (e.g., H433K and N434F). In one embodiment, thepresent invention includes anti-PD-1 antibodies comprising an Fc domaincomprising a S108P mutation in the hinge region of IgG4 to promote dimerstabilization. All possible combinations of the foregoing Fc domainmutations, and other mutations within the antibody variable domainsdisclosed herein, are contemplated within the scope of the presentinvention.

The present invention also includes anti-PD-1 antibodies comprising achimeric heavy chain constant (C_(H)) region, wherein the chimeric C_(H)region comprises segments derived from the C_(H) regions of more thanone immunoglobulin isotype. For example, the antibodies of the inventionmay comprise a chimeric C_(H) region comprising part or all of a C_(H)2domain derived from a human IgG1, human IgG2 or human IgG4 molecule,combined with part or all of a C_(H)3 domain derived from a human IgG1,human IgG2 or human IgG4 molecule. According to certain embodiments, theantibodies of the invention comprise a chimeric C_(H) region having achimeric hinge region. For example, a chimeric hinge may comprise an“upper hinge” amino acid sequence (amino acid residues from positions216 to 227 according to EU numbering) derived from a human IgG1, a humanIgG2 or a human IgG4 hinge region, combined with a “lower hinge”sequence (amino acid residues from positions 228 to 236 according to EUnumbering) derived from a human IgG1, a human IgG2 or a human IgG4 hingeregion. According to certain embodiments, the chimeric hinge regioncomprises amino acid residues derived from a human IgG1 or a human IgG4upper hinge and amino acid residues derived from a human IgG2 lowerhinge. An antibody comprising a chimeric C_(H) region as describedherein may, in certain embodiments, exhibit modified Fc effectorfunctions without adversely affecting the therapeutic or pharmacokineticproperties of the antibody. (See, e.g., U.S. Ser. No. 14/170,166, filedJan. 31, 2014, the disclosure of which is hereby incorporated byreference in its entirety).

Biological Characteristics of the Antibodies

In general, the antibodies of the present invention function by bindingto PD-1. The present invention includes anti-PD-1 antibodies andantigen-binding fragments thereof that bind soluble monomeric or dimericPD-1 molecules with high affinity. For example, the present inventionincludes antibodies and antigen-binding fragments of antibodies thatbind monomeric PD-1 (e.g., at 25° C. or at 37° C.) with a K_(D) of lessthan about 50 nM as measured by surface plasmon resonance, e.g., usingthe assay format as defined in Example 3 herein. In certain embodiments,the antibodies or antigen-binding fragments thereof bind monomeric PD-1with a K_(D) of less than about 40 nM, less than about 30 nM, less thanabout 20 nM, less than about 10 nM less than about 5 nM, less than about2 nM or less than about 1 nM, as measured by surface plasmon resonance,e.g., using the assay format as defined in Example 3 herein, or asubstantially similar assay.

The present invention also includes antibodies and antigen-bindingfragments thereof that bind dimeric PD-1 (e.g., at 25° C. or at 37° C.)with a K_(D) of less than about 400 pM as measured by surface plasmonresonance, e.g., using the assay format as defined in Example 3 herein.In certain embodiments, the antibodies or antigen-binding fragmentsthereof bind dimeric PD-1 with a K_(D) of less than about 300 pM, lessthan about 250 pM, less than about 200 pM, less than about 100 pM, orless than about 50 pM, as measured by surface plasmon resonance, e.g.,using the assay format as defined in Example 3 herein, or asubstantially similar assay.

The present invention also includes antibodies or antigen-bindingfragments thereof that bind cynomolgus (Macaca fascicularis) PD-1 (e.g.,at 25° C. or at 37° C.) with a K_(D) of less than about 35 nM asmeasured by surface plasmon resonance, e.g., using the assay format asdefined in Example 3 herein. In certain embodiments, the antibodies orantigen-binding fragments thereof bind cynomolgus PD-1 with a K_(D) ofless than about 30 nM, less than about 20 nM, less than about 15 nM,less than about 10 nM, or less than about 5 nM, as measured by surfaceplasmon resonance, e.g., using the assay format as defined in Example 3herein, or a substantially similar assay.

The present invention also includes antibodies and antigen-bindingfragments thereof that bind PD-1 with a dissociative half-life (t½) ofgreater than about 1.1 minutes as measured by surface plasmon resonanceat 25° C. or 37° C., e.g., using an assay format as defined in Example 3herein, or a substantially similar assay. In certain embodiments, theantibodies or antigen-binding fragments of the present invention bindPD-1 with a t1/2 of greater than about 5 minutes, greater than about 10minutes, greater than about 30 minutes, greater than about 50 minutes,greater than about 60 minutes, greater than about 70 minutes, greaterthan about 80 minutes, greater than about 90 minutes, greater than about100 minutes, greater than about 200 minutes, greater than about 300minutes, greater than about 400 minutes, greater than about 500 minutes,greater than about 600 minutes, greater than about 700 minutes, greaterthan about 800 minutes, greater than about 900 minutes, greater thanabout 1000 minutes, or greater than about 1200 minutes, as measured bysurface plasmon resonance at 25° C. or 37° C., e.g., using an assayformat as defined in Example 3 herein (e.g., mAb-capture orantigen-capture format), or a substantially similar assay.

The present invention also includes antibodies or antigen-bindingfragments thereof that block PD-1 binding to PD-L1 with an IC50 of lessthan about 3 nM as determined using a ELISA-based immunoassay assay,e.g., as shown in Example 4, or a substantially similar assay. Thepresent invention also includes antibodies and antigen-binding fragmentsthereof that bind to PD-1 and enhance the binding of PD-1 to PD-L1.

In some embodiments, the antibodies of the present invention may bind tothe extracellular domain of PD-1 or to a fragment of the domain. In someembodiments, the antibodies of the present invention may bind to morethan one domain (cross-reactive antibodies). In certain embodiments, theantibodies of the present invention may bind to an epitope located inthe extracellular domain comprising amino acid residues 21-171 of PD-1(SEQ ID NO: 327). In one embodiment, the antibodies may bind to anepitope comprising one or more amino acids selected from the groupconsisting of amino acid residues 1-146 of SEQ ID NOs: 321-324.

In certain embodiments, the antibodies of the present invention mayfunction by blocking or inhibiting the PD-L1-binding activity associatedwith PD-1 by binding to any other region or fragment of the full lengthprotein, the amino acid sequence of which is shown in SEQ ID NO: 327. Incertain embodiments, the antibodies may attenuate or modulate theinteraction between PD-1 and PD-L1.

In certain embodiments, the antibodies of the present invention may bebi-specific antibodies. The bi-specific antibodies of the invention maybind one epitope in one domain and may also bind a second epitope in adifferent domain of PD-1. In certain embodiments, the bi-specificantibodies of the invention may bind two different epitopes in the samedomain. In one embodiment, the multi-specific antigen-binding moleculecomprises a first binding specificity wherein the first bindingspecificity comprises the extracellular domain or fragment thereof ofPD-L1; and a second binding specificity to another epitope of PD-1.

In one embodiment, the invention provides an isolated fully humanmonoclonal antibody or antigen-binding fragment thereof that binds toPD-1, wherein the antibody or fragment thereof exhibits one or more ofthe following characteristics: (i) comprises a HCVR having an amino acidsequence selected from the group consisting of SEQ ID NO: 2, 18, 34, 50,66, 82, 98, 114, 130, 146, 162, 178, 194, 210, 218, 226, 234, 242, 250,258, 266, 274, 282, 290, 298, 306, and 314, or a substantially similarsequence thereof having at least 90%, at least 95%, at least 98% or atleast 99% sequence identity; (ii) comprises a LCVR having an amino acidsequence selected from the group consisting of SEQ ID NO: 10, 26, 42,58, 74, 90, 106, 122, 138, 154, 170, 186, and 202, or a substantiallysimilar sequence thereof having at least 90%, at least 95%, at least 98%or at least 99% sequence identity; (iii) comprises a HCDR3 domain havingan amino acid sequence selected from the group consisting of SEQ ID NO:8, 24, 40, 56, 72, 88, 104, 120, 136, 152, 168, 184, 200, 216, 224, 232,240, 248, 256, 264, 272, 280, 288, 296, 304, 312, and 320, or asubstantially similar sequence thereof having at least 90%, at least95%, at least 98% or at least 99% sequence identity; and a LCDR3 domainhaving an amino acid sequence selected from the group consisting of SEQID NO: 16, 32, 48, 64, 80, 96, 112, 128, 144, 160, 176, 192, and 208, ora substantially similar sequence thereof having at least 90%, at least95%, at least 98% or at least 99% sequence identity; (iv) comprises aHCDR1 domain having an amino acid sequence selected from the groupconsisting of SEQ ID NO: 4, 20, 36, 52, 68, 84, 100, 116, 132, 148, 164,180, 196, 212, 220, 228, 236, 244, 252, 260, 268, 276, 284, 292, 300,308, and 316, or a substantially similar sequence thereof having atleast 90%, at least 95%, at least 98% or at least 99% sequence identity;a HCDR2 domain having an amino acid sequence selected from the groupconsisting of SEQ ID NO: 6, 22, 38, 54, 70, 86, 102, 118, 134, 150, 166,182, 198, 214, 222, 230, 238, 246, 254, 262, 270, 278, 286, 294, 302,310, and 318, or a substantially similar sequence thereof having atleast 90%, at least 95%, at least 98% or at least 99% sequence identity;a LCDR1 domain having an amino acid sequence selected from the groupconsisting of SEQ ID NO: 12, 28, 44, 60, 76, 92, 108, 124, 140, 156,172, 188, and 204, or a substantially similar sequence thereof having atleast 90%, at least 95%, at least 98% or at least 99% sequence identity;and a LCDR2 domain having an amino acid sequence selected from the groupconsisting of SEQ ID NO: 14, 30, 46, 62, 78, 94, 110, 126, 142, 158,174, 190, and 206, or a substantially similar sequence thereof having atleast 90%, at least 95%, at least 98% or at least 99% sequence identity;(v) is a multi-specific antigen-binding molecule comprising a firstbinding specificity to PD-1 and a second binding specificity to anantigen selected from the group consisting of PD-1, a tumor specificantigen, an autoimmune tissue specific antigen, a virally infected cellantigen, a different T-cell co-inhibitor, T-cell receptor, and a Fcreceptor; (vi) binds to human PD-1 with a K_(D) of about 28 pM to about1.5 μM; (vii) binds to cynomolgus PD-1 with a K_(D) of about 3 nM toabout 7.5 μM; (viii) blocks or enhances the binding of PD-1 to PD-L1with an 1050 about 3.3 nM; (ix) blocks PD-1-induced T-cell downregulation and/or rescues T-cell signaling in a T-cell/APC luciferasereporter assay; (x) stimulates T-cell proliferation and activity in amixed lymphocyte reaction (MLR) assay; (xi) induces IL-2 and/or IFNγproduction in a MLR assay; and (xii) suppresses tumor growth andincreases survival in subjects with cancer.

In one embodiment, the invention provides an isolated fully humanmonoclonal antibody or antigen-binding fragment thereof that blocks PD-1binding to PD-L1, wherein the antibody or fragment thereof exhibits oneor more of the following characteristics: (i) comprises a HCVR having anamino acid sequence selected from the group consisting of SEQ ID NO:130, 162, 234 and 314, or a substantially similar sequence thereofhaving at least 90%, at least 95%, at least 98% or at least 99% sequenceidentity; (ii) comprises a LCVR having an amino acid sequence selectedfrom the group consisting of SEQ ID NO: 138, 170, 186, and 202, or asubstantially similar sequence thereof having at least 90%, at least95%, at least 98% or at least 99% sequence identity; (iii) comprises aHCDR3 domain having an amino acid sequence selected from the groupconsisting of SEQ ID NO: 136, 168, 240, and 320, or a substantiallysimilar sequence thereof having at least 90%, at least 95%, at least 98%or at least 99% sequence identity; and a LCDR3 domain having an aminoacid sequence selected from the group consisting of SEQ ID NO: 144, 176,192, and 208, or a substantially similar sequence thereof having atleast 90%, at least 95%, at least 98% or at least 99% sequence identity;(iv) comprises a HCDR1 domain having an amino acid sequence selectedfrom the group consisting of SEQ ID NO: 132, 164, 236, and 316, or asubstantially similar sequence thereof having at least 90%, at least95%, at least 98% or at least 99% sequence identity; a HCDR2 domainhaving an amino acid sequence selected from the group consisting of SEQID NO: 134, 166, 238, and 318, or a substantially similar sequencethereof having at least 90%, at least 95%, at least 98% or at least 99%sequence identity; a LCDR1 domain having an amino acid sequence selectedfrom the group consisting of SEQ ID NO: 140, 172, 188, and 204, or asubstantially similar sequence thereof having at least 90%, at least95%, at least 98% or at least 99% sequence identity; and a LCDR2 domainhaving an amino acid sequence selected from the group consisting of SEQID NO: 142, 174, 190, and 206, or a substantially similar sequencethereof having at least 90%, at least 95%, at least 98% or at least 99%sequence identity; (v) is a multi-specific antigen-binding moleculecomprising a first binding specificity to PD-1 and a second bindingspecificity to an antigen selected from the group consisting of adifferent epitope of PD-1, a tumor specific antigen, an autoimmunetissue specific antigen, a virally infected cell antigen, a differentT-cell co-inhibitor, T-cell receptor, and a Fc receptor; (vi) binds tohuman PD-1 with a K_(D)≤10⁻⁹M; (vii) binds to cynomolgus PD-1 with aK_(D)≤10⁻⁸M; (viii) blocks the binding of PD-1 to PD-L1 with anIC50≤10⁻¹° M; (ix) blocks PD-1-induced T-cell down regulation and/orrescues T-cell signaling in a T-cell/APC luciferase reporter assay; (x)stimulates T-cell proliferation and activity in a mixed lymphocytereaction (MLR) assay; (xi) induces IL-2 and/or IFNγ production in a MLRassay; and (xii) suppresses tumor growth and increases survival insubjects with cancer.

The antibodies of the present invention may possess one or more of theaforementioned biological characteristics, or any combinations thereof.Other biological characteristics of the antibodies of the presentinvention will be evident to a person of ordinary skill in the art froma review of the present disclosure including the working Examplesherein.

Species Selectivity and Species Cross-Reactivity

According to certain embodiments of the invention, the anti-PD-1antibodies bind to human PD-1 but not to PD-1 from other species.Alternatively, the anti-PD-1 antibodies of the invention, in certainembodiments, bind to human PD-1 and to PD-1 from one or more non-humanspecies. For example, the anti-PD-1 antibodies of the invention may bindto human PD-1 and may bind or not bind, as the case may be, to one ormore of mouse, rat, guinea pig, hamster, gerbil, pig, cat, dog, rabbit,goat, sheep, cow, horse, camel, cynomolgus, marmoset, rhesus orchimpanzee PD-1. In certain embodiments, the anti-PD-1 antibodies of theinvention may bind to human and cynomolgus PD-1 with the same affinitiesor with different affinities, but do not bind to rat and mouse PD-1.

Epitope Mapping and Related Technologies

The present invention includes anti-PD-1 antibodies which interact withone or more amino acids found within one or more domains of the PD-1molecule including, e.g., extracellular (IgV-like) domain, atransmembrane domain, and an intracellular domain containing theimmunoreceptor tyrosine-based inhibition motif (ITIM) and immunoreceptortyrosine-based switch motif (ITSM). The epitope to which the antibodiesbind may consist of a single contiguous sequence of 3 or more (e.g., 3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more)amino acids located within any of the aforementioned domains of the PD-1molecule (e.g. a linear epitope in a domain). Alternatively, the epitopemay consist of a plurality of non-contiguous amino acids (or amino acidsequences) located within either or both of the aforementioned domainsof the PD-1 molecule (e.g. a conformational epitope).

Various techniques known to persons of ordinary skill in the art can beused to determine whether an antibody “interacts with one or more aminoacids” within a polypeptide or protein. Exemplary techniques include,for example, routine cross-blocking assays, such as that described inAntibodies, Harlow and Lane (Cold Spring Harbor Press, Cold SpringHarbor, N.Y.). Other methods include alanine scanning mutationalanalysis, peptide blot analysis (Reineke (2004) Methods Mol. Biol. 248:443-63), peptide cleavage analysis crystallographic studies and NMRanalysis. In addition, methods such as epitope excision, epitopeextraction and chemical modification of antigens can be employed (Tomer(2000) Prot. Sci. 9: 487-496). Another method that can be used toidentify the amino acids within a polypeptide with which an antibodyinteracts is hydrogen/deuterium exchange detected by mass spectrometry.In general terms, the hydrogen/deuterium exchange method involvesdeuterium-labeling the protein of interest, followed by binding theantibody to the deuterium-labeled protein. Next, the protein/antibodycomplex is transferred to water and exchangeable protons within aminoacids that are protected by the antibody complex undergodeuterium-to-hydrogen back-exchange at a slower rate than exchangeableprotons within amino acids that are not part of the interface. As aresult, amino acids that form part of the protein/antibody interface mayretain deuterium and therefore exhibit relatively higher mass comparedto amino acids not included in the interface. After dissociation of theantibody, the target protein is subjected to protease cleavage and massspectrometry analysis, thereby revealing the deuterium-labeled residueswhich correspond to the specific amino acids with which the antibodyinteracts. See, e.g., Ehring (1999) Analytical Biochemistry 267:252-259; Engen and Smith (2001) Anal. Chem. 73: 256A-265A.

The term “epitope” refers to a site on an antigen to which B and/or Tcells respond. B-cell epitopes can be formed both from contiguous aminoacids or noncontiguous amino acids juxtaposed by tertiary folding of aprotein. Epitopes formed from contiguous amino acids are typicallyretained on exposure to denaturing solvents, whereas epitopes formed bytertiary folding are typically lost on treatment with denaturingsolvents. An epitope typically includes at least 3, and more usually, atleast 5 or 8-10 amino acids in a unique spatial conformation.

Modification-Assisted Profiling (MAP), also known as AntigenStructure-based Antibody Profiling (ASAP) is a method that categorizeslarge numbers of monoclonal antibodies (mAbs) directed against the sameantigen according to the similarities of the binding profile of eachantibody to chemically or enzymatically modified antigen surfaces (seeUS 2004/0101920, herein specifically incorporated by reference in itsentirety). Each category may reflect a unique epitope either distinctlydifferent from or partially overlapping with epitope represented byanother category. This technology allows rapid filtering of geneticallyidentical antibodies, such that characterization can be focused ongenetically distinct antibodies. When applied to hybridoma screening,MAP may facilitate identification of rare hybridoma clones that producemAbs having the desired characteristics. MAP may be used to sort theantibodies of the invention into groups of antibodies binding differentepitopes.

In certain embodiments, the anti-PD-1 antibodies or antigen-bindingfragments thereof bind an epitope within any one or more of the regionsexemplified in PD-1, either in natural form, as exemplified in SEQ IDNO: 327, or recombinantly produced, as exemplified in SEQ ID NOS:321-324, or to a fragment thereof. In some embodiments, the antibodiesof the invention bind to an extracellular region comprising one or moreamino acids selected from the group consisting of amino acid residues21-171 of PD-1. In some embodiments, the antibodies of the inventionbind to an extracellular region comprising one or more amino acidsselected from the group consisting of amino acid residues 1-146 ofcynomolgus PD-1, as exemplified by SEQ ID NO: 322.

In certain embodiments, the antibodies of the invention, as shown inTable 1, interact with at least one amino acid sequence selected fromthe group consisting of amino acid residues ranging from about position21 to about position 136 of SEQ ID NO: 327; or amino acid residuesranging from about position 136 to about position 171 of SEQ ID NO: 327.These regions are partially exemplified in SEQ ID NOs: 321-324.

The present invention includes anti-PD-1 antibodies that bind to thesame epitope, or a portion of the epitope, as any of the specificexemplary antibodies described herein in Table 1, or an antibody havingthe CDR sequences of any of the exemplary antibodies described inTable 1. Likewise, the present invention also includes anti-PD-1antibodies that compete for binding to PD-1 or a PD-1 fragment with anyof the specific exemplary antibodies described herein in Table 1, or anantibody having the CDR sequences of any of the exemplary antibodiesdescribed in Table 1. For example, the present invention includesanti-PD-1 antibodies that cross-compete for binding to PD-1 with one ormore antibodies as defined in Example 6 herein (e.g., H2aM7788N,H4xH8992P, H4xH8999P, H1M7799N, H2aM7780N, H1M7800N, H2aM7794N,H2aM7798N, H4xH9145P2, H4H9057P2, H4xH9120P2, H4xH9128P2, H4H9019P,H4xH9119P2, H4xH9135P2, H4xH9034P, H2aM7790N, H4xH9035P, H4xH9037P,H4xH9045P and H2aM7795N).

One can easily determine whether an antibody binds to the same epitopeas, or competes for binding with, a reference anti-PD-1 antibody byusing routine methods known in the art. For example, to determine if atest antibody binds to the same epitope as a reference anti-PD-1antibody of the invention, the reference antibody is allowed to bind toa PD-1 protein or peptide under saturating conditions. Next, the abilityof a test antibody to bind to the PD-1 molecule is assessed. If the testantibody is able to bind to PD-1 following saturation binding with thereference anti-PD-1 antibody, it can be concluded that the test antibodybinds to a different epitope than the reference anti-PD-1 antibody. Onthe other hand, if the test antibody is not able to bind to the PD-1protein following saturation binding with the reference anti-PD-1antibody, then the test antibody may bind to the same epitope as theepitope bound by the reference anti-PD-1 antibody of the invention.

To determine if an antibody competes for binding with a referenceanti-PD-1 antibody, the above-described binding methodology is performedin two orientations: In a first orientation, the reference antibody isallowed to bind to a PD-1 protein under saturating conditions followedby assessment of binding of the test antibody to the PD-1 molecule. In asecond orientation, the test antibody is allowed to bind to a PD-1molecule under saturating conditions followed by assessment of bindingof the reference antibody to the PD-1 molecule. If, in bothorientations, only the first (saturating) antibody is capable of bindingto the PD-1 molecule, then it is concluded that the test antibody andthe reference antibody compete for binding to PD-1. As will beappreciated by a person of ordinary skill in the art, an antibody thatcompetes for binding with a reference antibody may not necessarily bindto the identical epitope as the reference antibody, but may stericallyblock binding of the reference antibody by binding an overlapping oradjacent epitope.

Two antibodies bind to the same or overlapping epitope if eachcompetitively inhibits (blocks) binding of the other to the antigen.That is, a 1-, 5-, 10-, 20- or 100-fold excess of one antibody inhibitsbinding of the other by at least 50% but preferably 75%, 90% or even 99%as measured in a competitive binding assay (see, e.g., Junghans et al.,Cancer Res. 1990 50:1495-1502). Alternatively, two antibodies have thesame epitope if essentially all amino acid mutations in the antigen thatreduce or eliminate binding of one antibody reduce or eliminate bindingof the other. Two antibodies have overlapping epitopes if some aminoacid mutations that reduce or eliminate binding of one antibody reduceor eliminate binding of the other.

Additional routine experimentation (e.g., peptide mutation and bindinganalyses) can then be carried out to confirm whether the observed lackof binding of the test antibody is in fact due to binding to the sameepitope as the reference antibody or if steric blocking (or anotherphenomenon) is responsible for the lack of observed binding. Experimentsof this sort can be performed using ELISA, RIA, surface plasmonresonance, flow cytometry or any other quantitative or qualitativeantibody-binding assay available in the art.

Immunoconjugates

The invention encompasses a human anti-PD-1 monoclonal antibodyconjugated to a therapeutic moiety (“immunoconjugate”), such as acytotoxin or a chemotherapeutic agent to treat cancer. As used herein,the term “immunoconjugate” refers to an antibody which is chemically orbiologically linked to a cytotoxin, a radioactive agent, a cytokine, aninterferon, a target or reporter moiety, an enzyme, a toxin, a peptideor protein or a therapeutic agent. The antibody may be linked to thecytotoxin, radioactive agent, cytokine, interferon, target or reportermoiety, enzyme, toxin, peptide or therapeutic agent at any locationalong the molecule so long as it is able to bind its target. Examples ofimmunoconjugates include antibody drug conjugates and antibody-toxinfusion proteins. In one embodiment, the agent may be a second differentantibody to PD-1. In certain embodiments, the antibody may be conjugatedto an agent specific for a tumor cell or a virally infected cell. Thetype of therapeutic moiety that may be conjugated to the anti-PD-1antibody and will take into account the condition to be treated and thedesired therapeutic effect to be achieved. Examples of suitable agentsfor forming immunoconjugates are known in the art; see for example, WO05/103081.

Multi-specific Antibodies

The antibodies of the present invention may be mono-specific,bi-specific, or multi-specific. Multi-specific antibodies may bespecific for different epitopes of one target polypeptide or may containantigen-binding domains specific for more than one target polypeptide.See, e.g., Tutt et al., 1991, J. Immunol. 147:60-69; Kufer et al., 2004,Trends Biotechnol. 22:238-244.

In one aspect, the present invention includes multi-specificantigen-binding molecules or antigen-binding fragments thereof whereinone specificity of an immunoglobulin is specific for the extracellulardomain of PD-1, or a fragment thereof, and the other specificity of theimmunoglobulin is specific for binding outside the extracellular domainof PD-1, or a second therapeutic target, or is conjugated to atherapeutic moiety. In certain embodiments, the first antigen-bindingspecificity may comprise PD-L1 or PD-L2, or a fragment thereof. Incertain embodiments of the invention, one specificity of animmunoglobulin is specific for an epitope comprising amino acid residues21-171 of PD-1 (SEQ ID NO: 327) or a fragment thereof, and the otherspecificity of the immunoglobulin is specific for a second targetantigen. The second target antigen may be on the same cell as PD-1 or ona different cell. In one embodiment, the second target cell is on animmune cell other than a T-cell such as a B-cell, antigen-presentingcell, monocyte, macrophage, or dendritic cell. In some embodiments, thesecond target antigen may be present on a tumor cell or an autoimmunetissue cell or on a virally infected cell.

In another aspect, the invention provides multi-specific antigen-bindingmolecules or antigen-binding fragments thereof comprising a firstantigen-binding specificity that binds to PD-1 and a secondantigen-binding specificity that binds to a T-cell receptor, a B-cellreceptor or a Fc receptor. In a related aspect, the invention providesmulti-specific antigen-binding molecules or antigen-binding fragmentsthereof comprising a first antigen-binding specificity that binds toPD-1 and a second antigen-binding specificity that binds to a differentT-cell co-inhibitor such as LAG-3, CTLA-4, BTLA, CD-28, 2B4, LY108,TIGIT, TIM3, LAIR1, ICOS and CD160.

In another aspect, the invention provides multi-specific antigen-bindingmolecules or antigen-binding fragments thereof comprising a firstantigen-binding specificity that binds to PD-1 and a secondantigen-binding specificity that binds to an autoimmune tissue-specificantigen. In certain embodiments, the antibodies may be activating oragonist antibodies.

Any of the multi-specific antigen-binding molecules of the invention, orvariants thereof, may be constructed using standard molecular biologicaltechniques (e.g., recombinant DNA and protein expression technology), aswill be known to a person of ordinary skill in the art.

In some embodiments, PD-1-specific antibodies are generated in abi-specific format (a “bi-specific”) in which variable regions bindingto distinct domains of PD-1 are linked together to confer dual-domainspecificity within a single binding molecule. Appropriately designedbi-specifics may enhance overall PD-1 inhibitory efficacy throughincreasing both specificity and binding avidity. Variable regions withspecificity for individual domains, (e.g., segments of the N-terminaldomain), or that can bind to different regions within one domain, arepaired on a structural scaffold that allows each region to bindsimultaneously to the separate epitopes, or to different regions withinone domain. In one example for a bi-specific, heavy chain variableregions (V_(H)) from a binder with specificity for one domain arerecombined with light chain variable regions (V_(L)) from a series ofbinders with specificity for a second domain to identify non-cognateV_(L) partners that can be paired with an original V_(H) withoutdisrupting the original specificity for that V_(H). In this way, asingle V_(L) segment (e.g., V_(L)1) can be combined with two differentV_(H) domains (e.g., V_(H)1 and V_(H)2) to generate a bi-specificcomprised of two binding “arms” (V_(H)1-V_(L)1 and V_(H)2-V_(L)1). Useof a single V_(L) segment reduces the complexity of the system andthereby simplifies and increases efficiency in cloning, expression, andpurification processes used to generate the bi-specific (See, forexample, U.S. Ser. No. 13/022,759 and US2010/0331527).

Alternatively, antibodies that bind more than one domains and a secondtarget, such as, but not limited to, for example, a second differentanti-PD-1 antibody, may be prepared in a bi-specific format usingtechniques described herein, or other techniques known to those skilledin the art. Antibody variable regions binding to distinct regions may belinked together with variable regions that bind to relevant sites on,for example, the extracellular domain of PD-1, to confer dual-antigenspecificity within a single binding molecule. Appropriately designedbi-specifics of this nature serve a dual function. Variable regions withspecificity for the extracellular domain are combined with a variableregion with specificity for outside the extracellular domain and arepaired on a structural scaffold that allows each variable region to bindto the separate antigens.

An exemplary bi-specific antibody format that can be used in the contextof the present invention involves the use of a first immunoglobulin (Ig)C_(H)3 domain and a second Ig C_(H)3 domain, wherein the first andsecond Ig C_(H)3 domains differ from one another by at least one aminoacid, and wherein at least one amino acid difference reduces binding ofthe bi-specific antibody to Protein A as compared to a bi-specificantibody lacking the amino acid difference. In one embodiment, the firstIg C_(H)3 domain binds Protein A and the second Ig C_(H)3 domaincontains a mutation that reduces or abolishes Protein A binding such asan H95R modification (by IMGT exon numbering; H435R by EU numbering).The second C_(H)3 may further comprise a Y96F modification (by IMGT;Y436F by EU). Further modifications that may be found within the secondC_(H)3 include: D16E, L18M, N44S, K52N, V57M, and V821 (by IMGT; D356E,L358M, N384S, K392N, V397M, and V422I by EU) in the case of IgG1antibodies; N44S, K52N, and V821 (IMGT; N384S, K392N, and V422I by EU)in the case of IgG2 antibodies; and Q15R, N44S, K52N, V57M, R69K, E79Q,and V821 (by IMGT; Q355R, N384S, K392N, V397M, R409K, E419Q, and V422Iby EU) in the case of IgG4 antibodies. Variations on the bi-specificantibody format described above are contemplated within the scope of thepresent invention.

Other exemplary bispecific formats that can be used in the context ofthe present invention include, without limitation, e.g., scFv-based ordiabody bispecific formats, IgG-scFv fusions, dual variable domain(DVD)-Ig, Quadroma, knobs-into-holes, common light chain (e.g., commonlight chain with knobs-into-holes, etc.), CrossMab, CrossFab,(SEED)body, leucine zipper, Duobody, IgG1/IgG2, dual acting Fab(DAF)-IgG, and Mab² bispecific formats (see, e.g., Klein et al. 2012,mAbs 4:6, 1-11, and references cited therein, for a review of theforegoing formats). Bispecific antibodies can also be constructed usingpeptide/nucleic acid conjugation, e.g., wherein unnatural amino acidswith orthogonal chemical reactivity are used to generate site-specificantibody-oligonucleotide conjugates which then self-assemble intomultimeric complexes with defined composition, valency and geometry.(See, e.g., Kazane et al., J. Am. Chem. Soc. [Epub: Dec. 4, 2012]).

Therapeutic Administration and Formulations

The invention provides therapeutic compositions comprising the anti-PD-1antibodies or antigen-binding fragments thereof of the presentinvention. Therapeutic compositions in accordance with the inventionwill be administered with suitable carriers, excipients, and otheragents that are incorporated into formulations to provide improvedtransfer, delivery, tolerance, and the like. A multitude of appropriateformulations can be found in the formulary known to all pharmaceuticalchemists: Remington's Pharmaceutical Sciences, Mack Publishing Company,Easton, Pa. These formulations include, for example, powders, pastes,ointments, jellies, waxes, oils, lipids, lipid (cationic or anionic)containing vesicles (such as LIPOFECTIN™), DNA conjugates, anhydrousabsorption pastes, oil-in-water and water-in-oil emulsions, emulsionscarbowax (polyethylene glycols of various molecular weights), semi-solidgels, and semi-solid mixtures containing carbowax. See also Powell etal. “Compendium of excipients for parenteral formulations” PDA (1998) JPharm Sci Technol 52:238-311.

The dose of antibody may vary depending upon the age and the size of asubject to be administered, target disease, conditions, route ofadministration, and the like. When an antibody of the present inventionis used for treating a disease or disorder in an adult patient, or forpreventing such a disease, it is advantageous to administer the antibodyof the present invention normally at a single dose of about 0.1 to about60 mg/kg body weight, more preferably about 5 to about 60, about 10 toabout 50, or about 20 to about 50 mg/kg body weight. Depending on theseverity of the condition, the frequency and the duration of thetreatment can be adjusted. In certain embodiments, the antibody orantigen-binding fragment thereof of the invention can be administered asan initial dose of at least about 0.1 mg to about 800 mg, about 1 toabout 500 mg, about 5 to about 300 mg, or about 10 to about 200 mg, toabout 100 mg, or to about 50 mg. In certain embodiments, the initialdose may be followed by administration of a second or a plurality ofsubsequent doses of the antibody or antigen-binding fragment thereof inan amount that can be approximately the same or less than that of theinitial dose, wherein the subsequent doses are separated by at least 1day to 3 days; at least one week, at least 2 weeks; at least 3 weeks; atleast 4 weeks; at least 5 weeks; at least 6 weeks; at least 7 weeks; atleast 8 weeks; at least 9 weeks; at least 10 weeks; at least 12 weeks;or at least 14 weeks.

Various delivery systems are known and can be used to administer thepharmaceutical composition of the invention, e.g., encapsulation inliposomes, microparticles, microcapsules, recombinant cells capable ofexpressing the mutant viruses, receptor mediated endocytosis (see, e.g.,Wu et al. (1987) J. Biol. Chem. 262:4429-4432). Methods of introductioninclude, but are not limited to, intradermal, transdermal,intramuscular, intraperitoneal, intravenous, subcutaneous, intranasal,epidural and oral routes. The composition may be administered by anyconvenient route, for example by infusion or bolus injection, byabsorption through epithelial or mucocutaneous linings (e.g., oralmucosa, rectal and intestinal mucosa, etc.) and may be administeredtogether with other biologically active agents. Administration can besystemic or local. The pharmaceutical composition can be also deliveredin a vesicle, in particular a liposome (see, for example, Langer (1990)Science 249:1527-1533).

The use of nanoparticles to deliver the antibodies of the presentinvention is also contemplated herein. Antibody-conjugated nanoparticlesmay be used both for therapeutic and diagnostic applications.Antibody-conjugated nanoparticles and methods of preparation and use aredescribed in detail by Arruebo, M., et al. 2009 (“Antibody-conjugatednanoparticles for biomedical applications” in J. Nanomat. Volume 2009,Article ID 439389, 24 pages, doi: 10.1155/2009/439389), incorporatedherein by reference. Nanoparticles may be developed and conjugated toantibodies contained in pharmaceutical compositions to target tumorcells or autoimmune tissue cells or virally infected cells.Nanoparticles for drug delivery have also been described in, forexample, U.S. Pat. No. 8,257,740, or U.S. Pat. No. 8,246,995, eachincorporated herein in its entirety.

In certain situations, the pharmaceutical composition can be deliveredin a controlled release system. In one embodiment, a pump may be used.In another embodiment, polymeric materials can be used. In yet anotherembodiment, a controlled release system can be placed in proximity ofthe composition's target, thus requiring only a fraction of the systemicdose.

The injectable preparations may include dosage forms for intravenous,subcutaneous, intracutaneous, intracranial, intraperitoneal andintramuscular injections, drip infusions, etc. These injectablepreparations may be prepared by methods publicly known. For example, theinjectable preparations may be prepared, e.g., by dissolving, suspendingor emulsifying the antibody or its salt described above in a sterileaqueous medium or an oily medium conventionally used for injections. Asthe aqueous medium for injections, there are, for example, physiologicalsaline, an isotonic solution containing glucose and other auxiliaryagents, etc., which may be used in combination with an appropriatesolubilizing agent such as an alcohol (e.g., ethanol), a polyalcohol(e.g., propylene glycol, polyethylene glycol), a nonionic surfactant[e.g., polysorbate 80, HCO-50 (polyoxyethylene (50 mol) adduct ofhydrogenated castor oil)], etc. As the oily medium, there are employed,e.g., sesame oil, soybean oil, etc., which may be used in combinationwith a solubilizing agent such as benzyl benzoate, benzyl alcohol, etc.The injection thus prepared is preferably filled in an appropriateampoule.

A pharmaceutical composition of the present invention can be deliveredsubcutaneously or intravenously with a standard needle and syringe. Inaddition, with respect to subcutaneous delivery, a pen delivery devicereadily has applications in delivering a pharmaceutical composition ofthe present invention. Such a pen delivery device can be reusable ordisposable. A reusable pen delivery device generally utilizes areplaceable cartridge that contains a pharmaceutical composition. Onceall of the pharmaceutical composition within the cartridge has beenadministered and the cartridge is empty, the empty cartridge can readilybe discarded and replaced with a new cartridge that contains thepharmaceutical composition. The pen delivery device can then be reused.In a disposable pen delivery device, there is no replaceable cartridge.Rather, the disposable pen delivery device comes prefilled with thepharmaceutical composition held in a reservoir within the device. Oncethe reservoir is emptied of the pharmaceutical composition, the entiredevice is discarded.

Numerous reusable pen and autoinjector delivery devices haveapplications in the subcutaneous delivery of a pharmaceuticalcomposition of the present invention. Examples include, but certainlyare not limited to AUTOPEN™ (Owen Mumford, Inc., Woodstock, UK),DISETRONIC™ pen (Disetronic Medical Systems, Burghdorf, Switzerland),HUMALOG MIX 75/25™ pen, HUMALOG™ pen, HUMALIN 70/30™ pen (Eli Lilly andCo., Indianapolis, Ind.), NOVOPEN™ I, II and III (Novo Nordisk,Copenhagen, Denmark), NOVOPEN JUNIOR™ (Novo Nordisk, Copenhagen,Denmark), BD™ pen (Becton Dickinson, Franklin Lakes, N.J.), OPTIPEN™,OPTIPEN PRO™, OPTIPEN STARLET™, and OPTICLIK™ (Sanofi-Aventis,Frankfurt, Germany), to name only a few. Examples of disposable pendelivery devices having applications in subcutaneous delivery of apharmaceutical composition of the present invention include, butcertainly are not limited to the SOLOSTAR™ pen (Sanofi-Aventis), theFLEXPEN™ (Novo Nordisk), and the KW IKPEN™ (Eli Lilly), the SURECLICK™Autoinjector (Amgen, Thousand Oaks, Calif.), the PENLET™ (Haselmeier,Stuttgart, Germany), the EPIPEN (Dey, L.P.) and the HUMIRA™ Pen (AbbottLabs, Abbott Park, Ill.), to name only a few.

Advantageously, the pharmaceutical compositions for oral or parenteraluse described above are prepared into dosage forms in a unit dose suitedto fit a dose of the active ingredients. Such dosage forms in a unitdose include, for example, tablets, pills, capsules, injections(ampoules), suppositories, etc. The amount of the antibody contained isgenerally about 5 to about 500 mg per dosage form in a unit dose;especially in the form of injection, it is preferred that the antibodyis contained in about 5 to about 100 mg and in about 10 to about 250 mgfor the other dosage forms.

Therapeutic Uses of the Antibodies

The antibodies of the invention are useful, inter alia, for thetreatment, prevention and/or amelioration of any disease or disorderassociated with or mediated by PD-1 expression, signaling, or activity,or treatable by blocking the interaction between PD-1 and a PD-1 ligand(e.g., PD-L1, or PD-L2) or otherwise inhibiting PD-1 activity and/orsignaling. For example, the present invention provides methods fortreating cancer (tumor growth inhibition), chronic viral infectionsand/or autoimmune disease by administering an anti-PD-1 antibody (orpharmaceutical composition comprising an anti-PD-1 antibody) asdescribed herein to a patient in need of such treatment. The antibodiesof the present invention are useful for the treatment, prevention,and/or amelioration of disease or disorder or condition such as cancer,autoimmune disease or a viral infection and/or for ameliorating at leastone symptom associated with such disease, disorder or condition. In thecontext of the methods of treatment described herein, the anti-PD-1antibody may be administered as a monotherapy (i.e., as the onlytherapeutic agent) or in combination with one or more additionaltherapeutic agents (examples of which are described elsewhere herein).

In some embodiments of the invention, the antibodies described hereinare useful for treating subjects suffering from primary or recurrentcancer, including, but not limited to, renal cell carcinoma, colorectalcancer, non-small-cell lung cancer, brain cancer (e.g., glioblastomamultiforme), squamous cell carcinoma of head and neck, gastric cancer,prostate cancer, ovarian cancer, kidney cancer, breast cancer, multiplemyeloma, and melanoma.

The antibodies may be used to treat early stage or late-stage symptomsof cancer. In one embodiment, an antibody or fragment thereof of theinvention may be used to treat metastatic cancer. The antibodies areuseful in reducing or inhibiting or shrinking tumor growth of both solidtumors and blood cancers. In certain embodiments, treatment with anantibody or antigen-binding fragment thereof of the invention leads tomore than 50% regression, more than 60% regression, more than 70%regression, more than 80% regression or more than 90% regression of atumor in a subject. In certain embodiments, the antibodies may be usedto prevent relapse of a tumor. In certain embodiments, the antibodiesare useful in extending overall survival in a subject with cancer. Insome embodiments, the antibodies are useful in reducing toxicity due tochemotherapy or radiotherapy while maintaining long-term survival in apatient suffering from cancer.

In certain embodiments, the antibodies of the invention are useful totreat subjects suffering from a chronic viral infection. In someembodiments, the antibodies of the invention are useful in decreasingviral titers in the host and/or rescuing exhausted T-cells. In certainembodiments, an antibody or fragment thereof of the invention may beused to treat chronic viral infection by lymphocytic choriomeningitisvirus (LCMV). In some embodiments, an antibody or antigen-bindingfragment thereof the invention may be administered at a therapeutic doseto a patient with an infection by human immunodeficiency virus (HIV) orhuman papilloma virus (HPV) or hepatitis B/C virus (HBV/HCV). In arelated embodiment, an antibody or antigen-binding fragment thereof ofthe invention may be used to treat an infection by simianimmunodeficiency virus (SIV) in a simian subject such as cynomolgus.

In certain embodiments, a blocking antibody of the present invention maybe administered in a therapeutically effective amount to a subjectsuffering from a cancer or a viral infection.

In certain embodiments, the antibodies of the invention are useful fortreating an autoimmune disease, including but not limited to, alopeciaareata, autoimmune hepatitis, celiac disease, Graves' disease,Guillain-Barre syndrome, Hashimoto's disease, hemolytic anemia,inflammatory bowel disease, inflammatory myopathies, multiple sclerosis,primary biliary cirrhosis, psoriasis, rheumatoid arthritis, scleroderma,Sjögren's syndrome, systemic lupus erthyematosus, vitiligo, autoimmunepancreatitis, autoimmune urticaria, autoimmune thrombocytopenic purpura,Crohn's disease, diabetes type I, eosinophilic fasciitis, eosinophilicenterogastritis, Goodpasture's syndrome, myasthenia gravis, psoriaticarthritis, rheumatic fever, ulcerative colitis, vasculitis and Wegener'sgranulomatosis. In certain embodiments, an activating antibody of theinvention may be used to treat a subject suffering from autoimmunedisease.

One or more antibodies of the present invention may be administered torelieve or prevent or decrease the severity of one or more of thesymptoms or conditions of the disease or disorder.

It is also contemplated herein to use one or more antibodies of thepresent invention prophylactically to patients at risk for developing adisease or disorder such as cancer, autoimmune disease and chronic viralinfection.

In a further embodiment of the invention the present antibodies are usedfor the preparation of a pharmaceutical composition for treatingpatients suffering from cancer, autoimmune disease or viral infection.In another embodiment of the invention, the present antibodies are usedas adjunct therapy with any other agent or any other therapy known tothose skilled in the art useful for treating cancer, autoimmune diseaseor viral infection.

Combination Therapies and Formulations

Combination therapies may include an anti-PD-1 antibody of the inventionand any additional therapeutic agent that may be advantageously combinedwith an antibody of the invention, or with a biologically activefragment of an antibody of the invention.

The antibodies of the present invention may be combined synergisticallywith one or more anti-cancer drugs or therapy used to treat cancer,including, for example, renal cell carcinoma, colorectal cancer,glioblastoma multiforme, squamous cell carcinoma of head and neck,non-small-cell lung cancer, colon cancer, ovarian cancer,adenocarcinoma, prostate cancer, glioma, and melanoma. It iscontemplated herein to use anti-PD-1 antibodies of the invention incombination with immunostimulatory and/or immunosupportive therapies toinhibit tumor growth, and/or enhance survival of cancer patients. Theimmunostimulatory therapies include direct immunostimulatory therapiesto augment immune cell activity by either “releasing the brake” onsuppressed immune cells or “stepping on the gas” to activate an immuneresponse. Examples include targeting other checkpoint receptors,vaccination and adjuvants. The immunosupportive modalities may increaseantigenicity of the tumor by promoting immunogenic cell death,inflammation or have other indirect effects that promote an anti-tumorimmune response. Examples include radiation, chemotherapy,anti-angiogenic agents, and surgery.

In various embodiments, one or more antibodies of the present inventionmay be used in combination with an antibody to PD-L1, a second antibodyto PD-1 (e.g., nivolumab), a LAG-3 inhibitor, a CTLA-4 inhibitor (e.g.,ipilimumab), a TIM3 inhibitor, a BTLA inhibitor, a TIGIT inhibitor, aCD47 inhibitor, an antagonist of another T-cell co-inhibitor or ligand(e.g., an antibody to CD-28, 2B4, LY108, LAIR1, ICOS, CD160 or VISTA),an indoleamine-2,3-dioxygenase (IDO) inhibitor, a vascular endothelialgrowth factor (VEGF) antagonist [e.g., a “VEGF-Trap” such as afliberceptor other VEGF-inhibiting fusion protein as set forth in U.S. Pat. No.7,087,411, or an anti-VEGF antibody or antigen binding fragment thereof(e.g., bevacizumab, or ranibizumab) or a small molecule kinase inhibitorof VEGF receptor (e.g., sunitinib, sorafenib, or pazopanib)], an Ang2inhibitor (e.g., nesvacumab), a transforming growth factor beta (TGFβ)inhibitor, an epidermal growth factor receptor (EGFR) inhibitor (e.g.,erlotinib, cetuximab), an agonist to a co-stimulatory receptor (e.g., anagonist to glucocorticoid-induced TNFR-related protein), an antibody toa tumor-specific antigen (e.g., CA9, CA125, melanoma-associated antigen3 (MAGE3), carcinoembryonic antigen (CEA), vimentin, tumor-M2-PK,prostate-specific antigen (PSA), mucin-1, MART-1, and CA19-9), a vaccine(e.g., Bacillus Calmette-Guerin, a cancer vaccine), an adjuvant toincrease antigen presentation (e.g., granulocyte-macrophagecolony-stimulating factor), a bispecific antibody (e.g., CD3×CD20bispecific antibody, PSMA×CD3 bispecific antibody), a cytotoxin, achemotherapeutic agent (e.g., dacarbazine, temozolomide,cyclophosphamide, docetaxel, doxorubicin, daunorubicin, cisplatin,carboplatin, gemcitabine, methotrexate, mitoxantrone, oxaliplatin,paclitaxel, and vincristine), cyclophosphamide, radiotherapy, an IL-6Rinhibitor (e.g., sarilumab), an IL-4R inhibitor (e.g., dupilumab), anIL-10 inhibitor, a cytokine such as IL-2, IL-7, IL-21, and IL-15, anantibody-drug conjugate (ADC) (e.g., anti-CD19-DM4 ADC, and anti-DS6-DM4ADC), an anti-inflammatory drug (e.g., corticosteroids, andnon-steroidal anti-inflammatory drugs), a dietary supplement such asanti-oxidants or any palliative care to treat cancer. In certainembodiments, the anti-PD-1 antibodies of the present invention may beused in combination with cancer vaccines including dendritic cellvaccines, oncolytic viruses, tumor cell vaccines, etc. to augment theanti-tumor response. Examples of cancer vaccines that can be used incombination with anti-PD-1 antibodies of the present invention includeMAGE3 vaccine for melanoma and bladder cancer, MUC1 vaccine for breastcancer, EGFRv3 (e.g., Rindopepimut) for brain cancer (includingglioblastoma multiforme), or ALVAC-CEA (for CEA+ cancers).

In certain embodiments, the anti-PD-1 antibodies of the invention may beadministered in combination with radiation therapy in methods togenerate long-term durable anti-tumor responses and/or enhance survivalof patients with cancer. In some embodiments, the anti-PD-1 antibodiesof the invention may be administered prior to, concomitantly or afteradministering radiation therapy to a cancer patient. For example,radiation therapy may be administered in one or more doses to tumorlesions followed by administration of one or more doses of anti-PD-1antibodies of the invention. In some embodiments, radiation therapy maybe administered locally to a tumor lesion to enhance the localimmunogenicity of a patient's tumor (adjuvinating radiation) and/or tokill tumor cells (ablative radiation) followed by systemicadministration of an anti-PD-1 antibody of the invention. For example,intracranial radiation may be administered to a patient with braincancer (e.g., glioblastoma multiforme) in combination with systemicadministration of an anti-PD-1 antibody of the invention. In certainembodiments, the anti-PD-1 antibodies of the invention may beadministered in combination with radiation therapy and achemotherapeutic agent (e.g., temozolomide) or a VEGF antagonist (e.g.,aflibercept).

In certain embodiments, the anti-PD-1 antibodies of the invention may beadministered in combination with one or more anti-viral drugs to treatchronic viral infection caused by LCMV, HIV, HPV, HBV or HCV. Examplesof anti-viral drugs include, but are not limited to, zidovudine,lamivudine, abacavir, ribavirin, lopinavir, efavirenz, cobicistat,tenofovir, rilpivirine and corticosteroids. In some embodiments, theanti-PD-1 antibodies of the invention may be administered in combinationwith a LAG3 inhibitor, a CTLA-4 inhibitor or any antagonist of anotherT-cell co-inhibitor to treat chronic viral infection.

In certain embodiments, the anti-PD-1 antibodies of the invention may becombined with an antibody to a Fc receptor on immune cells for thetreatment of an autoimmune disease. In one embodiment, an antibody orfragment thereof of the invention is administered in combination with anantibody or antigen-binding protein targeted to an antigen specific toautoimmune tissue. In certain embodiments, an antibody orantigen-binding fragment thereof of the invention is administered incombination with an antibody or antigen-binding protein targeted to aT-cell receptor or a B-cell receptor, including but not limited to, Fcα(e.g., CD89), Fcγ (e.g., CD64, CD32, CD16a, and CD16b), CD19, etc. Theantibodies of fragments thereof of the invention may be used incombination with any drug or therapy known in the art (e.g.,corticosteroids and other immunosuppressants) to treat an autoimmunedisease or disorder including, but not limited to alopecia areata,autoimmune hepatitis, celiac disease, Graves' disease, Guillain-Barresyndrome, Hashimoto's disease, hemolytic anemia, inflammatory boweldisease, inflammatory myopathies, multiple sclerosis, primary biliarycirrhosis, psoriasis, rheumatoid arthritis, scleroderma, Sjögren'ssyndrome, systemic lupus erthyematosus, vitiligo, autoimmunepancreatitis, autoimmune urticaria, autoimmune thrombocytopenic purpura,Crohn's disease, diabetes type I, eosinophilic fasciitis, eosinophilicenterogastritis, Goodpasture's syndrome, myasthenia gravis, psoriaticarthritis, rheumatic fever, ulcerative colitis, vasculitis and Wegener'sgranulomatosis.

The additional therapeutically active agent(s)/component(s) may beadministered prior to, concurrent with, or after the administration ofthe anti-PD-1 antibody of the present invention. For purposes of thepresent disclosure, such administration regimens are considered theadministration of an anti-PD-1 antibody “in combination with” a secondtherapeutically active component.

The additional therapeutically active component(s) may be administeredto a subject prior to administration of an anti-PD-1 antibody of thepresent invention. For example, a first component may be deemed to beadministered “prior to” a second component if the first component isadministered 1 week before, 72 hours before, 60 hours before, 48 hoursbefore, 36 hours before, 24 hours before, 12 hours before, 6 hoursbefore, 5 hours before, 4 hours before, 3 hours before, 2 hours before,1 hour before, 30 minutes before, 15 minutes before, 10 minutes before,5 minutes before, or less than 1 minute before administration of thesecond component. In other embodiments, the additional therapeuticallyactive component(s) may be administered to a subject afteradministration of an anti-PD-1 antibody of the present invention. Forexample, a first component may be deemed to be administered “after” asecond component if the first component is administered 1 minute after,5 minutes after, 10 minutes after, 15 minutes after, 30 minutes after, 1hour after, 2 hours after, 3 hours after, 4 hours after, 5 hours after,6 hours after, 12 hours after, 24 hours after, 36 hours after, 48 hoursafter, 60 hours after, 72 hours after administration of the secondcomponent. In yet other embodiments, the additional therapeuticallyactive component(s) may be administered to a subject concurrent withadministration of an anti-PD-1 antibody of the present invention.“Concurrent” administration, for purposes of the present invention,includes, e.g., administration of an anti-PD-1 antibody and anadditional therapeutically active component to a subject in a singledosage form (e.g., co-formulated), or in separate dosage formsadministered to the subject within about 30 minutes or less of eachother. If administered in separate dosage forms, each dosage form may beadministered via the same route (e.g., both the anti-PD-1 antibody andthe additional therapeutically active component may be administeredintravenously, subcutaneously, etc.); alternatively, each dosage formmay be administered via a different route (e.g., the anti-PD-1 antibodymay be administered intravenously, and the additional therapeuticallyactive component may be administered subcutaneously). In any event,administering the components in a single dosage from, in separate dosageforms by the same route, or in separate dosage forms by different routesare all considered “concurrent administration,” for purposes of thepresent disclosure. For purposes of the present disclosure,administration of an anti-PD-1 antibody “prior to”, “concurrent with,”or “after” (as those terms are defined herein above) administration ofan additional therapeutically active component is consideredadministration of an anti-PD-1 antibody “in combination with” anadditional therapeutically active component).

The present invention includes pharmaceutical compositions in which ananti-PD-1 antibody of the present invention is co-formulated with one ormore of the additional therapeutically active component(s) as describedelsewhere herein using a variety of dosage combinations.

In exemplary embodiments in which an anti-PD-1 antibody of the inventionis administered in combination with a VEGF antagonist (e.g., a VEGF trapsuch as aflibercept), including administration of co-formulationscomprising an anti-PD-1 antibody and a VEGF antagonist, the individualcomponents may be administered to a subject and/or co-formulated using avariety of dosage combinations. For example, the anti-PD-1 antibody maybe administered to a subject and/or contained in a co-formulation in anamount selected from the group consisting of 0.01 mg, 0.02 mg, 0.03 mg,0.04 mg, 0.05 mg, 0.1 mg, 0.2 mg, 0.3 mg, 0.4 mg, 0.5 mg, 0.6 mg, 0.7mg, 0.8 mg, 0.9 mg, 1.0 mg, 1.5 mg, 2.0 mg, 2.5 mg, 3.0 mg, 3.5 mg, 4.0mg, 4.5 mg, 5.0 mg, 6.0 mg, 7.0 mg, 8.0 mg, 9.0 mg, and 10.0 mg; and theVEGF antagonist (e.g., a VEGF trap such as aflibercept) may beadministered to the subject and/or contained in a co-formulation in anamount selected from the group consisting of 0.1 mg, 0.2 mg, 0.3 mg, 0.4mg, 0.5 mg, 0.6 mg, 0.7 mg, 0.8 mg, 0.9 mg, 1.0 mg, 1.1 mg, 1.2 mg, 1.3mg, 1.4 mg, 1.5 mg, 1.6 mg, 1.7 mg, 1.8 mg, 1.9 mg, 2.0 mg, 2.1 mg, 2.2mg, 2.3 mg, 2.4 mg, 2.5 mg, 2.6 mg, 2.7 mg, 2.8 mg, 2.9 mg and 3.0 mg.The combinations/co-formulations may be administered to a subjectaccording to any of the administration regimens disclosed elsewhereherein, including, e.g., twice a week, once every week, once every 2weeks, once every 3 weeks, once every month, once every 2 months, onceevery 3 months, once every 4 months, once every 5 months, once every 6months, etc.

Administrative Regimens

According to certain embodiments of the present invention, multipledoses of an anti-PD-1 antibody (or a pharmaceutical compositioncomprising a combination of an anti-PD-1 antibody and any of theadditional therapeutically active agents mentioned herein) may beadministered to a subject over a defined time course. The methodsaccording to this aspect of the invention comprise sequentiallyadministering to a subject multiple doses of an anti-PD-1 antibody ofthe invention. As used herein, “sequentially administering” means thateach dose of anti-PD-1 antibody is administered to the subject at adifferent point in time, e.g., on different days separated by apredetermined interval (e.g., hours, days, weeks or months). The presentinvention includes methods which comprise sequentially administering tothe patient a single initial dose of an anti-PD-1 antibody, followed byone or more secondary doses of the anti-PD-1 antibody, and optionallyfollowed by one or more tertiary doses of the anti-PD-1 antibody. Theanti-PD-1 antibody may be administered at a dose between 0.1 mg/kg to100 mg/kg.

The terms “initial dose,” “secondary doses,” and “tertiary doses,” referto the temporal sequence of administration of the anti-PD-1 antibody ofthe invention. Thus, the “initial dose” is the dose which isadministered at the beginning of the treatment regimen (also referred toas the “baseline dose”); the “secondary doses” are the doses which areadministered after the initial dose; and the “tertiary doses” are thedoses which are administered after the secondary doses. The initial,secondary, and tertiary doses may all contain the same amount ofanti-PD-1 antibody, but generally may differ from one another in termsof frequency of administration. In certain embodiments, however, theamount of anti-PD-1 antibody contained in the initial, secondary and/ortertiary doses varies from one another (e.g., adjusted up or down asappropriate) during the course of treatment. In certain embodiments, twoor more (e.g., 2, 3, 4, or 5) doses are administered at the beginning ofthe treatment regimen as “loading doses” followed by subsequent dosesthat are administered on a less frequent basis (e.g., “maintenancedoses”).

In certain exemplary embodiments of the present invention, eachsecondary and/or tertiary dose is administered 1 to 26 (e.g., 1, 1½, 2,2½, 3, 3½, 4, 4½, 5, 5½, 6, 6½, 7, 7½, 8, 8½, 9, 9½, 10, 10½, 11, 11½,12, 12½, 13, 13½, 14, 14½, 15, 15½, 16, 16½, 17, 17½, 18, 18½, 19, 19½,20, 20½, 21, 21½, 22, 22½, 23, 23½, 24, 24½, 25, 25½, 26, 26½, or more)weeks after the immediately preceding dose. The phrase “the immediatelypreceding dose,” as used herein, means, in a sequence of multipleadministrations, the dose of anti-PD-1 antibody which is administered toa patient prior to the administration of the very next dose in thesequence with no intervening doses.

The methods according to this aspect of the invention may compriseadministering to a patient any number of secondary and/or tertiary dosesof an anti-PD-1 antibody. For example, in certain embodiments, only asingle secondary dose is administered to the patient. In otherembodiments, two or more (e.g., 2, 3, 4, 5, 6, 7, 8, or more) secondarydoses are administered to the patient. Likewise, in certain embodiments,only a single tertiary dose is administered to the patient. In otherembodiments, two or more (e.g., 2, 3, 4, 5, 6, 7, 8, or more) tertiarydoses are administered to the patient.

In embodiments involving multiple secondary doses, each secondary dosemay be administered at the same frequency as the other secondary doses.For example, each secondary dose may be administered to the patient 1 to2 weeks or 1 to 2 months after the immediately preceding dose.Similarly, in embodiments involving multiple tertiary doses, eachtertiary dose may be administered at the same frequency as the othertertiary doses. For example, each tertiary dose may be administered tothe patient 2 to 12 weeks after the immediately preceding dose. Incertain embodiments of the invention, the frequency at which thesecondary and/or tertiary doses are administered to a patient can varyover the course of the treatment regimen. The frequency ofadministration may also be adjusted during the course of treatment by aphysician depending on the needs of the individual patient followingclinical examination.

The present invention includes administration regimens in which 2 to 6loading doses are administered to a patient at a first frequency (e.g.,once a week, once every two weeks, once every three weeks, once a month,once every two months, etc.), followed by administration of two or moremaintenance doses to the patient on a less frequent basis. For example,according to this aspect of the invention, if the loading doses areadministered at a frequency of, e.g., once a month (e.g., two, three,four, or more loading doses administered once a month), then themaintenance doses may be administered to the patient once every fiveweeks, once every six weeks, once every seven weeks, once every eightweeks, once every ten weeks, once every twelve weeks, etc.).

Diagnostic Uses of the Antibodies

The anti-PD-1 antibodies of the present invention may be used to detectand/or measure PD-1 in a sample, e.g., for diagnostic purposes. Someembodiments contemplate the use of one or more antibodies of the presentinvention in assays to detect a disease or disorder such as cancer,autoimmune disease or chronic viral infection. Exemplary diagnosticassays for PD-1 may comprise, e.g., contacting a sample, obtained from apatient, with an anti-PD-1 antibody of the invention, wherein theanti-PD-1 antibody is labeled with a detectable label or reportermolecule or used as a capture ligand to selectively isolate PD-1 frompatient samples. Alternatively, an unlabeled anti-PD-1 antibody can beused in diagnostic applications in combination with a secondary antibodywhich is itself detectably labeled. The detectable label or reportermolecule can be a radioisotope, such as ³H, ¹⁴C, ³²P, ³⁵S, or ¹²⁵I; afluorescent or chemiluminescent moiety such as fluoresceinisothiocyanate, or rhodamine; or an enzyme such as alkaline phosphatase,β-galactosidase, horseradish peroxidase, or luciferase. Specificexemplary assays that can be used to detect or measure PD-1 in a sampleinclude enzyme-linked immunosorbent assay (ELISA), radioimmunoassay(RIA), and fluorescence-activated cell sorting (FACS).

Samples that can be used in PD-1 diagnostic assays according to thepresent invention include any tissue or fluid sample obtainable from apatient, which contains detectable quantities of either PD-1 protein, orfragments thereof, under normal or pathological conditions. Generally,levels of PD-1 in a particular sample obtained from a healthy patient(e.g., a patient not afflicted with cancer or an autoimmune disease)will be measured to initially establish a baseline, or standard, levelof PD-1. This baseline level of PD-1 can then be compared against thelevels of PD-1 measured in samples obtained from individuals suspectedof having a cancer-related condition, or symptoms associated with suchcondition.

The antibodies specific for PD-1 may contain no additional labels ormoieties, or they may contain an N-terminal or C-terminal label ormoiety. In one embodiment, the label or moiety is biotin. In a bindingassay, the location of a label (if any) may determine the orientation ofthe peptide relative to the surface upon which the peptide is bound. Forexample, if a surface is coated with avidin, a peptide containing anN-terminal biotin will be oriented such that the C-terminal portion ofthe peptide will be distal to the surface.

Aspects of the invention relate to use of the disclosed antibodies asmarkers for predicting prognosis of cancer or an autoimmune disorder inpatients. Antibodies of the present invention may be used in diagnosticassays to evaluate prognosis of cancer in a patient and to predictsurvival.

EXAMPLES

The following examples are put forth so as to provide those of ordinaryskill in the art with a complete disclosure and description of how tomake and use the methods and compositions of the invention, and are notintended to limit the scope of what the inventors regard as theirinvention. Efforts have been made to ensure accuracy with respect tonumbers used (e.g., amounts, temperature, etc.) but some experimentalerrors and deviations should be accounted for. Unless indicatedotherwise, parts are parts by weight, molecular weight is averagemolecular weight, temperature is in degrees Centigrade, room temperatureis about 25° C., and pressure is at or near atmospheric.

Example 1: Generation of Human Antibodies to PD-1

Human antibodies to PD-1 were generated using a fragment of PD-1 thatranges from about amino acids 25-170 of GenBank Accession NP_005009.2(SEQ ID NO: 327) with a C93S change. The immunogen was administereddirectly, with an adjuvant to stimulate the immune response, to aVELOCIMMUNE® mouse comprising DNA encoding human Immunoglobulin heavyand kappa light chain variable regions. The antibody immune response wasmonitored by a PD-1-specific immunoassay. When a desired immune responsewas achieved splenocytes were harvested and fused with mouse myelomacells to preserve their viability and form hybridoma cell lines. Thehybridoma cell lines were screened and selected to identify cell linesthat produce PD-1-specific antibodies. Using this technique, and theimmunogen described above, several anti-PD-1 chimeric antibodies (i.e.,antibodies possessing human variable domains and mouse constant domains)were obtained; exemplary antibodies generated in this manner weredesignated as H1M7789N, H1 M7799N, H1 M7800N, H2M7780N, H2M7788N,H2M7790N, H2M7791 N, H2M7794N, H2M7795N, H2M7796N, and H2M7798N.

Anti-PD-1 antibodies were also isolated directly from antigen-positive Bcells without fusion to myeloma cells, as described in U.S.2007/0280945A1, herein specifically incorporated by reference in itsentirety. Using this method, several fully human anti-PD-1 antibodies(i.e., antibodies possessing human variable domains and human constantdomains) were obtained; exemplary antibodies generated in this mannerwere designated as follows: H4H9019P, H4xH9034P2, H4xH9035P2,H4xH9037P2, H4xH9045P2, H4xH9048P2, H4H9057P2, H4H9068P2, H4xH9119P2,H4xH9120P2, H4xH9128P2, H4xH9135P2, H4xH9145P2, H4xH8992P, H4xH8999P,and H4xH9008P.

The biological properties of the exemplary antibodies generated inaccordance with the methods of this Example are described in detail inthe Examples set forth below.

Example 2: Heavy and Light Chain Variable Region Amino Acid andNucleotide Sequences

Table 1 sets forth the amino acid sequence identifiers of the heavy andlight chain variable regions and CDRs of selected anti-PD-1 antibodiesof the invention. The corresponding nucleic acid sequence identifiersare set forth in Table 2.

TABLE 1 Amino Acid Sequence Identifiers Antibody SEQ ID NOs: DesignationHCVR HCDR1 HCDR2 HCDR3 LCVR LCDR1 LCDR2 LCDR3 H1M7789N 2 4 6 8 10 12 1416 H1M7799N 18 20 22 24 26 28 30 32 H1M7800N 34 36 38 40 42 44 46 48H2M7780N 50 52 54 56 58 60 62 64 H2M7788N 66 68 70 72 74 76 78 80H2M7790N 82 84 86 88 90 92 94 96 H2M7791N 98 100 102 104 106 108 110 112H2M7794N 114 116 118 120 122 124 126 128 H2M7795N 130 132 134 136 138140 142 144 H2M7796N 146 148 150 152 154 156 158 160 H2M7798N 162 164166 168 170 172 174 176 H4H9019P 178 180 182 184 186 188 190 192 H4 ×H9034P2 194 196 198 200 202 204 206 208 H4 × H9035P2 210 212 214 216 202204 206 208 H4 × H9037P2 218 220 222 224 202 204 206 208 H4 × H9045P2226 228 230 232 202 204 206 208 H4 × H9048P2 234 236 238 240 202 204 206208 H4H9057P2 242 244 246 248 202 204 206 208 H4H9068P2 250 252 254 256202 204 206 208 H4 × H9119P2 258 260 262 264 202 204 206 208 H4 ×H9120P2 266 268 270 272 202 204 206 208 H4 × H9128P2 274 276 278 280 202204 206 208 H4 × H9135P2 282 284 286 288 202 204 206 208 H4 × H9145P2290 292 294 296 202 204 206 208 H4 × H8992P 298 300 302 304 186 188 190192 H4 × H8999P 306 308 310 312 186 188 190 192 H4 × H9008P 314 316 318320 186 188 190 192

TABLE 2 Nucleic Acid Sequence Identifiers Antibody SEQ ID NOs:Designation HCVR HCDR1 HCDR2 HCDR3 LCVR LCDR1 LCDR2 LCDR3 H1M7789N 1 3 57 9 11 13 15 H1M7799N 17 19 21 23 25 27 29 31 H1M7800N 33 35 37 39 41 4345 47 H2M7780N 49 51 53 55 57 59 61 63 H2M7788N 65 67 69 71 73 75 77 79H2M7790N 81 83 85 87 89 91 93 95 H2M7791N 97 99 101 103 105 107 109 111H2M7794N 113 115 117 119 121 123 125 127 H2M7795N 129 131 133 135 137139 141 143 H2M7796N 145 147 149 151 153 155 157 159 H2M7798N 161 163165 167 169 171 173 175 H4H9019P 177 179 181 183 185 187 189 191 H4 ×H9034P2 193 195 197 199 201 203 205 207 H4 × H9035P2 209 211 213 215 201203 205 207 H4 × H9037P2 217 219 221 223 201 203 205 207 H4 × H9045P2225 227 229 231 201 203 205 207 H4 × H9048P2 233 235 237 239 201 203 205207 H4H9057P2 241 243 245 247 201 203 205 207 H4H9068P2 249 251 253 255201 203 205 207 H4 × H9119P2 257 259 261 263 201 203 205 207 H4 ×H9120P2 265 267 269 271 201 203 205 207 H4 × H9128P2 273 275 277 279 201203 205 207 H4 × H9135P2 281 283 285 287 201 203 205 207 H4 × H9145P2289 291 293 295 201 203 205 207 H4 × H8992P 297 299 301 303 185 187 189191 H4 × H8999P 305 307 309 311 185 187 189 191 H4 × H9008P 313 315 317319 185 187 189 191

Antibodies are typically referred to herein according to the followingnomenclature: Fc prefix (e.g. “H4xH,” “H1 M,” “H2M,” etc.), followed bya numerical identifier (e.g. “7789,” “7799,” etc., as shown in Table 1),followed by a “P,” “P2,” “N,” or “B” suffix. Thus, according to thisnomenclature, an antibody may be referred to herein as, e.g.,“H1H7789N,” “H1 M7799N,” “H2M7780N,” etc. The H4xH, H1 M, H2M and H2aMprefixes on the antibody designations used herein indicate theparticular Fc region isotype of the antibody. For example, an “H4xH”antibody has a human IgG4 Fc with 2 or more amino acid changes asdisclosed in US20100331527, an “H1 M” antibody has a mouse IgG1 Fc, andan “H2M” antibody has a mouse IgG2 Fc (a or b isotype) (all variableregions are fully human as denoted by the first ‘H’ in the antibodydesignation). As will be appreciated by a person of ordinary skill inthe art, an antibody having a particular Fc isotype can be converted toan antibody with a different Fc isotype (e.g., an antibody with a mouseIgG1 Fc can be converted to an antibody with a human IgG4, etc.), but inany event, the variable domains (including the CDRs)—which are indicatedby the numerical identifiers shown in Table 1—will remain the same, andthe binding properties to antigen are expected to be identical orsubstantially similar regardless of the nature of the Fc domain.

In certain embodiments, selected antibodies with a mouse IgG1 Fc wereconverted to antibodies with human IgG4 Fc. In one embodiment, the IgG4Fc domain comprises a serine to proline mutation in the hinge region(S108P) to promote dimer stabilization. Table 3 sets forth the aminoacid sequence identifiers of heavy chain and light chain sequences ofselected anti-PD-1 antibodies with human IgG4 Fc.

TABLE 3 Antibody SEQ ID NOs: Designation Heavy Chain Light ChainH4H7798N 330 331 H4H7795N2 332 333 H4H9008P 334 335 H4H9048P2 336 337

Each heavy chain sequence in Table 3 comprised a variable region (V_(H)or HCVR; comprising HCDR1, HCDR2 and HCDR3) and a constant region(comprising C_(H)1, C_(H)2 and C_(H)3 domains). Each light chainsequence in Table 3 comprised a variable region (V_(L) or LCVR;comprising LCDR1, LCDR2 and LCDR3) and a constant region (C_(L)). SEQ IDNO: 330 comprised a HCVR comprising amino acids 1-117 and a constantregion comprising amino acids 118-444. SEQ ID NO: 331 comprised a LCVRcomprising amino acids 1-107 and a constant region comprising aminoacids 108-214. SEQ ID NO: 332 comprised a HCVR comprising amino acids1-122 and a constant region comprising amino acids 123-449. SEQ ID NO:333 comprised a LCVR comprising amino acids 1-107 and a constant regioncomprising amino acids 108-214. SEQ ID NO: 334 comprised a HCVRcomprising amino acids 1-119 and a constant region comprising aminoacids 120-446. SEQ ID NO: 335 comprised a LCVR comprising amino acids1-108 and a constant region comprising amino acids 109-215. SEQ ID NO:336 comprised a HCVR comprising amino acids 1-121 and a constant regioncomprising amino acids 122-448. SEQ ID NO: 337 comprised a LCVRcomprising amino acids 1-108 and a constant region comprising aminoacids 109-215.

Example 3: Antibody Binding to PD-1 as Determined by Surface PlasmonResonance

Binding association and dissociation rate constants (k_(a) and k_(d),respectively), equilibrium dissociation constants and dissociationhalf-lives (K_(D) and t½, respectively) for antigen binding to purifiedanti-PD1 antibodies were determined using a real-time surface plasmonresonance biosensor assay on a Biacore 4000 or Biacore T200 instrument.The Biacore sensor surface was derivatized with either a polyclonalrabbit anti-mouse antibody (GE, # BR-1008-38) or with a monoclonal mouseanti-human Fc antibody (GE, # BR-1008-39) to capture approximately100-900 RUs of anti-PD-1 monoclonal antibodies, expressed with either amouse Fc or a human Fc, respectively. The PD-1 reagents tested forbinding to the anti-PD-1 antibodies included recombinant human PD-1expressed with a C-terminal myc-myc-hexahistidine tag (hPD-1-MMH; SEQ IDNO: 321), recombinant cynomolgus monkey PD-1 expressed with a C-terminalmyc-myc-hexahistidine tag (MfPD-1-MMH; SEQ ID NO: 322), recombinanthuman PD-1 dimer expressed with either a C-terminal mouse IgG2a Fc tag(hPD-1-mFc; SEQ ID NO: 323) or with a C-terminal human IgG1 Fc(hPD1-hFc; SEQ ID NO: 324), and monkey PD-1 with mFc (SEQ ID NO: 329).Different concentrations of PD-1 reagents ranging from 200 nM to 3.7 nMwere injected over the anti-PD-1 monoclonal antibody captured surface ata flow rate of 304/min on Biacore 4000 or at 504/min on Biacore T200.The binding of the PD-1 reagents to captured monoclonal antibodies wasmonitored for 3 to 5 minutes while their dissociation from theantibodies was monitored for 7 to 10 minutes in HBST running buffer(0.01 M HEPES pH 7.4, 0.15 M NaCl, 3 mM EDTA, 0.05% v/v Surfactant P20).Experiments were performed at 25° C. and 37° C. Kinetic association(k_(a)) and dissociation (k_(d)) rate constants were determined byprocessing and fitting the data to a 1:1 binding model using Scrubber2.0c curve fitting software. Binding dissociation equilibrium constants(K_(D)) and dissociative half-lives (t_(1/2)) were then calculated fromthe kinetic rate constants as: K_(D) (M)=k_(d) k_(a) and t_(1/2)(min)=[ln2/(60*k_(d))]. Binding kinetics parameters for differentanti-PD-1 monoclonal antibodies binding to different PD-1 reagents at25° C. and 37° C. are tabulated in Tables 4-11.

TABLE 4 Binding Kinetics parameters of anti-PD-1 monoclonal antibodiesbinding to human PD-1-MMH at 25° C. k_(a) k_(d) K_(D) t½ Antibody (1/Ms)(1/s) (M) (min) H2aM7780N 9.32E+03 3.59E−04 3.85E−08 32 H2aM7788N1.97E+04 3.88E−04 1.96E−08 30 H1M7789N 2.53E+04 5.31E−05 2.10E−09 218H2aM7790N 4.63E+04 8.23E−04 1.78E−08 14 H2aM7791N 3.01E+04 7.06E−042.34E−08 16 H2aM7794N 5.50E+04 2.12E−03 3.80E−08 5.4 H2aM7795N 4.91E+041.15E−03 2.35E−08 10 H2aM7796N 6.73E+03 1.93E−03 2.86E−07 6.0 H2aM7798N1.32E+05 3.06E−04 2.31E−09 38 H1M7799N 5.04E+04 1.23E−02 2.44E−07 0.9H1M7800N 5.88E+04 9.47E−03 1.61E−07 1.2 H4H9019P 2.05E+04 8.08E−043.94E−08 14 H4xH9034P 1.02E+05 1.49E−03 1.45E−08 7.8 H4xH9035P 1.03E+054.75E−04 4.62E−09 24 H4xH9037P 7.32E+04 7.95E−04 1.09E−08 15 H4xH9045P5.40E+04 4.03E−03 7.46E−08 2.9 H4xH9048P2 1.37E+05 1.23E−03 8.95E−09 9.4H4H9057P2 4.60E+04 1.34E−02 2.91E−07 0.9 H4H9068P2 NB* NB* NB* NB*H4xH9119P2 7.84E+04 1.22E−03 1.56E−08 9.5 H4xH9120P2 3.32E+04 9.98E−043.01E−08 12 H4xH9128P2 4.95E+04 7.19E−04 1.45E−08 16 H4xH9135P2 1.17E+051.20E−03 1.02E−08 10 H4xH9145P2 3.47E+04 1.34E−03 3.85E−08 8.6 H4xH8992P1.50E+05 2.13E−02 1.41E−07 0.5 H4xH8999P 2.83E+05 1.23E−03 4.33E−09 9.4H4xH9008P 4.29E+04 1.33E−03 3.10E−08 8.7 H4H7795N2 6.35E+04 1.48E−032.33E−08 8 H4H7798N 1.47E+05 4.43E−04 3.01E−09 26 *NB indicates thatunder the experimental conditions, PD-1 reagent did not bind to thecaptured anti-PD-1 monoclonal antibody

TABLE 5 Binding Kinetics parameters of anti-PD-1 monoclonal antibodiesbinding to human PD-1-MMH at 37° C. k_(a) k_(d) K_(D) t½ Antibody (1/Ms)(1/s) (M) (min) H2aM7780N 2.72E+04 1.52E−03 5.58E−08 7.6 H2aM7788N2.88E+04 1.49E−03 5.19E−08 7.7 H1M7789N 4.53E+04 2.95E−04 6.52E−09 39H2aM7790N 6.13E+04 5.20E−03 8.49E−08 2.2 H2aM7791N 4.18E+04 2.24E−035.35E−08 5.2 H2aM7794N 1.20E+05 7.92E−03 6.61E−08 1.5 H2aM7795N 6.75E+044.58E−03 6.78E−08 2.5 H2aM7796N 1.09E+04 1.65E−02 1.51E−06 0.7 H2aM7798N1.73E+05 6.56E−04 3.79E−09 18 H1M7799N 7.94E+04 4.25E−02 5.36E−07 0.3H1M7800N 7.83E+04 3.99E−02 5.10E−07 0.3 H4H9019P 1.20E+04 5.44E−034.53E−07 2.1 H4xH9034P 2.79E+05 1.12E−02 4.02E−08 1.0 H4xH9035P 2.98E+054.26E−03 1.43E−08 2.7 H4xH9037P 2.26E+05 6.68E−03 2.95E−08 1.7 H4xH9045P8.04E+04 5.32E−02 6.62E−07 0.2 H4xH9048P2 3.70E+05 8.60E−03 2.32E−08 1.3H4H9057P2 NB* NB* NB* NB* H4H9068P2 NB* NB* NB* NB* H4xH9119P2 2.40E+051.04E−02 4.35E−08 1.1 H4xH9120P2 6.88E+04 7.01E−03 1.02E−07 1.6H4xH9128P2 1.04E+05 4.36E−03 4.20E−08 2.6 H4xH9135P2 4.18E+05 1.11E−022.66E−08 1.0 H4xH9145P2 1.31E+05 1.23E−02 9.40E−08 0.9 H4xH8992P IC* IC*IC* IC* H4xH8999P 5.99E+05 9.42E−03 1.57E−08 1.2 H4xH9008P 1.29E+058.09E−03 6.26E−08 1.4 H4H7795N2 6.41E+04 6.64E−03 1.04E−07 1.7 H4H7798N2.27E+05 1.70E−03 7.48E−09 7 *NB indicates that under the experimentalconditions, PD-1 reagent did not bind to the captured anti-PD-1monoclonal antibody. IC indicates that under the experimentalconditions, PD-1 binding is inconclusive.

TABLE 6 Binding Kinetics parameters of anti-PD-1 monoclonal antibodiesbinding to human PD-1 dimer (human PD-1-mFc or human PD-1-hFc) at 25° C.k_(a) k_(d) K_(D) t½ Antibody (1/Ms) (1/s) (M) (min) H2aM7780N 4.21E+049.94E−06 2.36E−10 1162 H2aM7788N 8.94E+04 2.82E−05 3.15E−10 410 H1M7789N3.91E+04 4.31E−05 1.10E−09 268 H2aM7790N 1.86E+05 3.02E−05 1.62E−10 383H2aM7791N 4.05E+04 1.01E−04 2.49E−09 114 H2aM7794N 1.79E+05 1.06E−045.93E−10 109 H2aM7795N 1.38E+05 3.14E−05 2.27E−10 368 H2aM7796N 2.61E+048.67E−05 3.32E−09 133 H2aM7798N 3.50E+05 2.29E−05 6.55E−11 505 H1M7799N2.38E+05 8.55E−05 3.60E−10 135 H1M7800N 1.52E+05 7.72E−05 5.09E−10 150H4H9019P 4.38E+04 8.61E−05 1.97E−09 134 H4xH9034P 2.15E+05 1.51E−047.01E−10 77 H4xH9035P 2.01E+05 1.03E−04 5.13E−10 112 H4xH9037P 1.50E+051.29E−04 8.62E−10 89 H4xH9045P 9.13E+04 1.60E−04 1.75E−09 72 H4xH9048P22.36E+05 1.88E−04 7.98E−10 61 H4H9057P2 1.01E+05 1.77E−04 1.75E−09 65H4H9068P2 4.72E+04 2.80E−03 5.94E−08 4 H4xH9119P2 1.63E+05 1.62E−049.92E−10 71 H4xH9120P2 6.52E+04 1.19E−04 1.82E−09 97 H4xH9128P2 8.37E+041.33E−04 1.59E−09 87 H4xH9135P2 2.12E+05 1.38E−04 6.51E−10 84 H4xH9145P26.58E+04 1.58E−04 2.40E−09 73 H4xH8992P 2.35E+05 1.60E−04 6.80E−10 72H4xH8999P 5.55E+05 1.20E−04 2.17E−10 96 H4xH9008P 3.52E+04 2.80E−057.96E−10 412 H4H7795N2 1.50E+05 9.25E−05 6.15E−10 125 H4H7798N 4.41E+055.40E−05 1.22E−10 214

TABLE 7 Binding Kinetics parameters of anti-PD-1 monoclonal antibodiesbinding to human PD-1 dimer (human PD-1-mFc or human PD-1-hFc) at 37° C.k_(a) k_(d) K_(D) t½ Antibody (1/Ms) (1/s) (M) (min) H2aM7780N 9.94E+042.29E−05 2.30E−10 505 H2aM7788N 1.31E+05 2.13E−05 1.63E−10 542 H1M7789N1.09E+05 ≤1.0E−05 ≤9.17E−11  ≥1155 H2aM7790N 2.01E+05 8.49E−05 4.22E−10136 H2aM7791N 4.98E+04 1.79E−04 3.59E−09 65 H2aM7794N 4.68E+05 2.11E−044.52E−10 55 H2aM7795N 1.65E+05 6.13E−05 3.71E−10 188 H2aM7796N 2.21E+044.34E−04 1.96E−08 27 H2aM7798N 4.90E+05 1.40E−05 2.80E−11 825 H1M7799N4.41E+05 1.81E−04 4.11E−10 64 H1M7800N 4.00E+05 1.81E−04 4.50E−10 64H4H9019P 7.17E+04 1.95E−04 2.71E−09 59 H4xH9034P 3.02E+05 6.30E−042.09E−09 18 H4xH9035P 3.16E+05 5.54E−04 1.75E−09 21 H4xH9037P 2.63E+059.21E−04 3.50E−09 13 H4xH9045P 2.14E+05 1.10E−03 5.13E−09 11 H4xH9048P23.61E+05 1.10E−03 3.05E−09 10 H4H9057P2 2.33E+05 2.11E−03 9.07E−09 5H4H9068P2 9.69E+04 1.20E−02 1.24E−07 1 H4xH9119P2 2.40E+05 9.09E−043.80E−09 13 H4xH9120P2 8.08E+04 4.82E−04 5.96E−09 24 H4xH9128P2 1.86E+056.86E−04 3.68E−09 17 H4xH9135P2 3.10E+05 7.02E−04 2.27E−09 16 H4xH9145P21.60E+05 5.71E−04 3.58E−09 20 H4xH8992P 3.49E+05 1.02E−03 2.91E−09 11H4xH8999P 7.57E+05 4.51E−04 5.96E−10 26 H4xH9008P 5.52E+04 ≤1.0E−05≤1.81E−10  ≥1155 H4H7795N2 1.60E+05 2.64E−04 1.65E−09 44 H4H7798N6.60E+05 1.15E−04 1.75E−10 100

TABLE 8 Binding Kinetics parameters of anti-PD-1 monoclonal antibodiesbinding to MfPD-1-MMH at 25° C. k_(a) k_(d) K_(D) t½ Antibody (1/Ms)(1/s) (M) (min) H2aM7780N 1.00E+04 3.15E−04 3.15E−08 37 H2aM7788N8.63E+03 6.62E−04 7.66E−08 17 H1M7789N 1.55E+04 1.23E−04 7.89E−09 94H2aM7790N 3.11E+04 9.37E−04 3.01E−08 12 H2aM7791N 1.61E+04 5.53E−043.44E−08 21 H2aM7794N 3.60E+04 5.99E−03 1.66E−07 1.9 H2aM7795N 4.44E+048.89E−04 2.01E−08 13 H2aM7796N NB* NB* NB* NB* H2aM7798N 8.72E+043.93E−04 4.50E−09 29 H1M7799N 5.78E+04 1.30E−02 2.24E−07 0.9 H1M7800N5.89E+04 1.04E−02 1.76E−07 1.1 H4H9019P 1.94E+04 8.33E−04 4.29E−08 14H4xH9034P 9.61E+04 2.69E−03 2.80E−08 4.3 H4xH9035P 9.36E+04 4.34E−044.64E−09 27 H4xH9037P 6.99E+04 9.15E−04 1.31E−08 13 H4xH9045P 6.25E+047.05E−03 1.13E−07 1.6 H4xH9048P2 1.28E+05 8.97E−04 7.00E−09 13 H4H9057P23.46E+04 1.91E−02 5.51E−07 0.6 H4H9068P2 NB* NB* NB* NB* H4xH9119P27.50E+04 1.66E−03 2.22E−08 6.9 H4xH9120P2 3.17E+04 1.08E−03 3.41E−08 11H4xH9128P2 3.68E+04 6.49E−04 1.77E−08 18 H4xH9135P2 1.24E+05 1.31E−031.06E−08 8.8 H4xH9145P2 2.86E+04 1.24E−03 4.31E−08 9.3 H4xH8992P1.88E+05 3.76E−02 2.00E−07 0.3 H4xH8999P 4.29E+05 1.33E−03 3.09E−09 8.7H4xH9008P 1.05E+05 2.49E−03 2.38E−08 4.6 H4H7795N2 6.59E+04 1.48E−032.24E−08 8 H4H7798N 1.43E+05 5.51E−04 3.86E−09 21 *NB indicates thatunder the experimental conditions, PD-1 reagent did not bind to thecaptured anti-PD-1 monoclonal antibody

TABLE 9 Binding Kinetics parameters of anti-PD-1 monoclonal antibodiesbinding to MfPD-1-MMH at 37° C. k_(a) k_(d) K_(D) t½ Antibody (1/Ms)(1/s) (M) (min) H2aM7780N 2.29E+04 1.38E−03 6.05E−08 8.3 H2aM7788N1.88E+04 3.28E−03 1.74E−07 3.5 H1M7789N 4.79E+04 4.08E−04 8.50E−09 28H2aM7790N 2.55E+04 6.93E−03 2.71E−07 1.7 H2aM7791N 3.79E+04 1.91E−035.05E−08 6.0 H2aM7794N 6.66E+04 2.01E−02 3.02E−07 0.6 H2aM7795N 6.47E+043.89E−03 6.02E−08 3.0 H2aM7796N NB* NB* NB* NB* H2aM7798N 1.42E+059.93E−04 7.00E−09 12 H1M7799N 8.80E+04 4.67E−02 5.30E−07 0.2 H1M7800N8.40E+04 4.43E−02 5.27E−07 0.3 H4H9019P 2.14E+04 7.63E−03 3.56E−07 1.5H4xH9034P 2.83E+05 2.47E−02 8.73E−08 0.5 H4xH9035P 3.06E+05 4.29E−031.40E−08 2.7 H4xH9037P 2.22E+05 8.80E−03 3.97E−08 1.3 H4xH9045P 1.40E+041.05E−01 7.54E−06 0.1 H4xH9048P2 4.15E+05 6.97E−03 1.68E−08 1.7H4H9057P2 NB* NB* NB* NB* H4H9068P2 NB* NB* NB* NB* H4xH9119P2 2.40E+051.23E−02 5.14E−08 0.9 H4xH9120P2 6.98E+04 7.48E−03 1.07E−07 1.5H4xH9128P2 9.06E+04 4.18E−03 4.61E−08 2.8 H4xH9135P2 4.62E+05 1.34E−022.89E−08 0.9 H4xH9145P2 1.71E+05 1.43E−02 8.37E−08 0.8 H4xH8992P IC* IC*IC* IC* H4xH8999P 9.83E+05 9.26E−03 9.41E−09 1.2 H4xH9008P 5.86E+051.38E−02 2.35E−08 0.8 H4H7795N2 7.80E+04 6.89E−03 8.83E−08 1.7 H4H7798N2.13E+05 2.23E−3  1.05E−08 5 *NB indicates that under the experimentalconditions, PD-1 reagent did not bind to the captured anti-PD-1monoclonal antibody. IC indicates that under the experimentalconditions, PD-1 binding is inconclusive.

TABLE 10 Binding Kinetics parameters of anti-PD-1 monoclonal antibodiesbinding to monkey PD-1 dimer (monkey PD-1-mFc) at 25° C. 100nM Amount ofMonkey mAb PD-1-mFc Captured Bound k_(a) k_(d) k_(D) t½ Antibody (RU)(RU) (1/Ms) (1/s) (M) (min) H4H9019P 116 31 4.55E+04 8.96E-05 1.97E−09129 H4 × H9034P 215 95 2.03E+05 1.66E−04 8.18E−10 70 H4 × H9035P 153 782.16E+05 9.96E−05 4.60E−10 116 H4 × H9037P 137 58 1.50E+05 1.37E−049.12E−10 84 H4 × H9045P 202 78 9.78E+04 1.68E−04 1.72E−09 69 H4 ×H9048P2 227 115 2.43E+05 1.84E−04 7.54E−10 63 H4H9057P2 196 75 1.02E+053.03E−04 2.98E−09 38 H4H9068P2 178 17 5.70E+04 3.09E−03 5.42E−08 4 H4 ×H9119P2 209 83 1.63E+05 1.72E−04 1.05E−09 67 H4 × H9120P2 195 525.84E+04 1.12E−04 1.91E−09 104 H4 × H9128P2 175 64 7.87E+04 1.24E−041.57E−09 94 H4 × H9135P2 150 74 2.38E+05 1.43E−04 6.02E−10 81 H4 ×H9145P2 304 84 7.24E+04 1.50E−04 2.08E−09 77 H4 × H8992P 260 1222.03E+05 2.51E−04 1.24E−09 46 H4 × H8999P 217 126 5.50E+05 1.15E−042.10E−10 100 H4 × H9008P 248 93 1.20E+05 5.77E−05 4.80E−10 200 H4H7795N2204 60 1.60E+05 9.92E−05 6.21E−10 116 H4H7798N 223 93 4.49E+05 6.14E−051.37E−10 188

TABLE 11 Binding Kinetics parameters of anti-PD-1 monoclonal antibodiesbinding to monkey PD-1 dimer (monkey PD-1-mFc) at 37° C. Amount of 100nM Monkey mAb Captured PD-1-mFc Bound k_(a) k_(d) K_(D) t½ Antibody (RU)(RU) (1/Ms) (1/s) (M) (min) H4H9019P 89 36 8.16E+04 2.59E−04 3.17E−09 45 H4xH9034P 184 81 3.07E+05 7.49E−04 2.44E−09  15 H4xH9035P 88 403.67E+05 6.23E−04 1.70E−09  19 H4xH9037P 55 24 2.80E+05 8.97E−043.21E−09  13 H4xH9045P 161 65 2.41E+05 1.36E−03 5.66E−09  8 H4xH9048P2184 84 4.94E+05 1.13E−03 2.29E−09  10 H4H9057P2 105 28 1.61E+05 4.77E−032.96E−08    2.4 H4H9068P2 90 6 1.21E+05 1.05E−02 8.63E−08    1.1H4xH9119P2 98 40 2.79E+05 8.85E−04 3.17E−09  13 H4xH9120P2 141 468.29E+04 5.02E−04 6.06E−09  23 H4xH9128P2 148 60 1.87E+05 8.16E−044.36E−09  14 H4xH9135P2 106 52 3.42E+05 7.94E−04 2.32E−09  15 H4xH9145P2284 94 1.51E+05 6.09E−04 4.04E−09  19 H4xH8992P 206 86 3.50E+05 1.53E−034.38E−09  8 H4xH8999P 160 83 7.30E+05 5.10E−04 7.00E−10  23 H4xH9008P216 98 2.04E+05  1.00E−05*  4.90E−11* 1155* H4H7795N2 164 47 1.70E+052.90E−04 1.71E−09  40 H4H7798N 203 88 6.30E+05 1.27E−04 2.02E−10  91*indicates that under the current experimental conditions, nodissociation of PD-1 reagent was observed and the value of kd wasmanually fixed at 1.00E−05

As shown in Table 4, at 25° C., 28 of the 29 anti-PD-1 antibodies of theinvention bound to hPD-1-MMH with K_(D) values ranging from 2.1 nM to291 nM. One antibody, H4H9068P2, did not demonstrate any measurablebinding to hPD-1-MMH at 25° C. As shown in Table 5, at 37° C., 26 of the29 anti-PD-1 antibodies of the invention bound to hPD-1-MMH with K_(D)values ranging from 3.79 nM to 1.51 μM. Three antibodies of theinvention did not demonstrate any conclusive binding to hPD-1-MMH at 37°C. As shown in Table 6, at 25° C., all 29 anti-PD-1 antibodies of theinvention bound to hPD-1 dimer proteins with K_(D) values ranging from65.5 pM to 59.4 nM. As shown in Table 7, at 37° C., all 27 anti-PD-1antibodies of the invention bound to hPD-1 dimer proteins with K_(D)values ranging from 3.09 pM to 551 nM. As shown in Table 8, at 25° C.,27 of the 29 anti-PD-1 antibodies of the invention bound to MfPD-1-MMHwith K_(D) values ranging from 3.09 nM to 551 nM. Two antibodies of theinvention did not demonstrate any conclusive binding to MfPD-1-MMH at25° C. As shown in Table 9, at 37° C., 25 of the 29 anti-PD-1 antibodiesof the invention bound to MfPD-1-MMH with K_(D) values ranging from 7.00nM to 7.54 μM. Four antibodies of the invention did not demonstrate anyconclusive binding to MfPD-1-MMH at 37° C. As shown in Table 10, at 25°C., all 18 of the tested anti-PD-1 antibodies of the invention bound toMfPD-1 dimer with K_(D) values ranging from 137 pM to 54.2 nM. As shownin Table 11, at 37° C., all 18 of the tested anti-PD-1 antibodies of theinvention bound to MfPD-1 dimer with K_(D) values ranging from less than49 pM to 86.3 nM.

Example 4: Blocking of PD-1 Binding to PD-L1 as Determined by ELISA

The ability of anti-PD-1 antibodies to block human PD-1 binding to itsligand, the PD-L1 receptor, was measured using three competitionsandwich ELISA formats. Dimeric human PD-L1 proteins, comprised of aportion of the human PD-L1 extracellular domain expressed with either aC-terminal human Fc tag (hPD-L1-hFc; SEQ ID: 325) or a C-terminal mouseFc tag (hPD-L1-mFc; SEQ ID: 326), or dimeric human PD-L2, comprised ofthe human PD-L2 extracellular region produced with a C-terminal human Fctag (hPD-L2-hFc; R&D Systems, #1224-PL) were separately coated at aconcentration of 2 μg/mL in PBS on a 96-well microtiter plate overnightat 4° C. Nonspecific binding sites were subsequently blocked using a0.5% (w/v) solution of BSA in PBS. In a first competition format, aconstant concentration of 1.5 nM of a dimeric human PD-1 protein,comprised of the human PD-1 extracellular domain expressed with aC-terminal mouse Fc tag (hPD-1-mFc; SEQ ID: 323) was added to serialdilutions of anti-PD-1 antibodies or isotype control antibodies so thatthe final concentrations of antibodies ranged from 0 to 200 nM. In asecond competition format, a constant concentration of 200 pM of dimericbiotinylated human PD-1 protein, comprised of the human PD-1extracellular domain that was expressed with a C-terminal human Fc tag(biot-hPD-1-hFc; SEQ ID: 323), was similarly added to serial dilutionsof anti-PD-1 antibodies or an isotype control at final antibodyconcentrations ranging from 0 to 50 nM. In a third competition format, aconstant concentration of 100 pM of dimeric hPD-1-mFc protein wassimilarly added to serial dilutions of anti-PD-1 antibodies or anisotype control at final antibody concentrations ranging from 0 to 100nM. These antibody-protein complexes were then incubated for 1 hour atroom temperature (RT). Antibody-protein complexes with 1.5 nM constanthPD-1-mFc were transferred to microtiter plates coated with hPD-L1-hFc,antibody-protein complexes with 200 pM constant biot-hPD-1-hFc weretransferred to hPD-L1-mFc coated plates, and antibody-protein complexeswith 100 pM constant hPD-1-mFc were transferred to microtiter platescoated with hPD-L2-hFc. After incubating for 1 hour at RT, the wellswere washed, and plate-bound hPD-1-mFc was detected with an anti-mFcpolyclonal antibody conjugated with horseradish peroxidase (HRP)(Jackson ImmunoResearch Inc., #115-035-164), and plate-boundbiot-hPD-1-hFc was detected with streptavidin conjugated with HRP(Thermo Scientific, # N200). Samples were developed with a TMB solution(BD Biosciences, #51-2606KC and #51-2607KC) to produce a colorimetricreaction and then color development was stabilized by addition of 1Msulfuric acid before measuring absorbance at 450 nm on a Victor X5 platereader. Data analysis was performed using a sigmoidal dose-responsemodel within Prism™ software (GraphPad). The calculated IC₅₀ value,defined as the concentration of antibody required to reduce 50% of humanPD-1 binding to human PD-L1 or PD-L2, was used as an indicator ofblocking potency. Percent maximum blockade was calculated as a measureof the ability of the antibodies to completely block binding of humanPD-1 to human PD-L1 or PD-L2 on the plate as determined from the dosecurve. This percent maximum blockade was calculated by subtracting from100% the ratio of the reduction in signal observed in the presence ofthe highest tested concentration for each antibody relative to thedifference between the signal observed for a sample of human PD-1containing no anti-PD-1 antibody (0% blocking) and the background signalfrom HRP-conjugated secondary antibody alone (100% blocking).

Percent maximum blockade and the calculated IC₅₀ values for antibodiesblocking greater than 35% of the hPD-1 binding signal are shown inTables 12-14. Antibodies that showed a decrease in the hPD-1 bindingsignal of 35% or less were defined as non-blockers. Antibodies thatshowed an increase of 35% or more in the binding signal of human PD-1were characterized as non-blocker/enhancers. The theoretical assaybottom, defined as the minimum antibody concentration theoreticallyneeded to occupy 50% binding sites of human PD-1 in the assay, is 0.75nM for the format using 1.5 nM constant hPD-1-mFc, 100 pM for the formatusing 200 pM constant biot-hPD-1-hFc, and 50 pM for the format using 100pM constant hPD-1-mFc, indicating that lower calculated IC₅₀ values maynot represent quantitative protein-antibody site binding. For thisreason, antibodies with calculated IC₅₀ values less than 0.75 nM in theassay with hPD-1-mFc constant and hPD-L1 coat, less than 100 pM in theassay with biot-hPD-1-hFc constant and hPD-L1 coat, and less than 50 pMin the assay with hPD-1-mFc constant and hPD-L2 coat are reported inTables 12-14 as <7.5E-10M, <1.0E-10M and <5.0E-11M, respectively.

TABLE 12 ELISA blocking of human PD-1 binding to human PD-L1 byanti-PD-1 antibodies 200 nM Antibody Blocking 1.5 nM of hPD- blocking1.5 nM 1-mFc binding to hPD- hPD-1-mFc binding to Antibody L1-hFc, IC₅₀(M) hPD-L1-hFc, % blocking H4H9019P 1.3E−09  98 H4xH9034P 5.1E−10* 98H4xH9045P 2.8E−10* 98 H4xH9048P2 3.3E−09  67 H4xH9120P2 1.0E−09  98H4xH9128P2 6.4E−10* 98 H4xH9035P 6.2E−10* 99 H4xH9135P2 1.1E−09  97H4xH9145P2 9.3E−10  90 H4xH9119P2 2.0E−10* 78 H4H9057P2 1.9E−10* 98H4H9068P2 NBI/Enchancer −142 H4xH9037P 8.9E−10  100 H2aM7780N 6.9E−10*94 H2aM7788N 2.2E−10* 74 H1M7789N NBI/Enchancer −170 H2aM7790N 1.5E−09 74 H2aM7791N NBI/Enchancer −154 H2aM7794N 1.1E−09  95 H2aM7795N28.6E−10  93 H2aM7796N NBI −20 H2aM7798N 6.8E−10* 93 H1M7799N 2.2E−10* 82H1M7800N 6.0E−10* 83 H4xH8992P 1.3E−09  93 H4xH8999P 1.3E−09  88H4xH9008P 2.4E−09  88 Isotype control 1 NBI −3 Isotype control 2 NBI −34Isotype control 2 NBI −7 Isotype control 2 NBI −16 Assay theoreticalbottom: for blocking ELISA with hPD-1-mFc constant and hPD-L1 coat is7.5E−10M *Below theoretical bottom of the assay; NT—not tested;NBI—non-blocker; NBI/Enhancer—non-blocker/enhancer; IC—inconclusive

TABLE 13 ELISA blocking of biotinylated human PD-1 binding to humanPD-L1 by anti-PD-1 antibodies 50 nM Antibody blocking Blocking 200 pMbiot- 200 pM biot-hPD-1-hFc hPD-1-hFc binding to binding to hPD-L1-mFc,Antibody hPD-L1-mFc, IC₅₀ (M) % blocking H4H9019P 6.4E−10  97 H4xH9034P6.6E−11* 96 H4xH9045P 1.3E−10  95 H4xH9048P2 IC 76 H4xH9120P2 3.9E−10 96 H4xH9128P2 1.9E−10  97 H4xH9035P 8.0E−11* 95 H4xH9135P2 1.5E−10  96H4xH9145P2 3.5E−10  97 H4xH9119P2 8.2E−11* 96 H4H9057P2 NBI/Enhancer −57H4H9068P2 NBI/Enhancer −43 H4xH9037P 7.8E−11* 95 H2aM7780N 9.1E−11* 100H2aM7788N 6.5E−11* 100 H1M7789N NBI 9 H2aM7790N 1.9E−10  99 H2aM7791NNBI / Enhancer −45 H2aM7794N 2.3E−10  99 H2aM7795N2 6.9E−11* 99H2aM7796N 1.3E−09  60 H2aM7798N 7.3E−11* 100 H1M7799N 5.9E−11* 100H1M7800N 6.5E−11* 99 H4xH8992P 1.6E−10  97 H4xH8999P 1.8E−10  92H4xH9008P 1.3E−09  93 Isotype control 1 NBI 19 Isotype control 2 NBI 35Isotype control 2 NBI −18 Isotype control 2 NBI −11 Assay theoreticalbottom: for blocking ELISA with biot-hPD-1-mFc constant and hPD-L1 coatis 1.0E−10M *Below theoretical bottom of the assay; NT—not tested;NBI—non-blocker; NBI/Enhancer—non-blocker/enhancer; IC—inconclusive

TABLE 14 ELISA blocking of human PD-1 binding to human PD-L2 byanti-PD-1 antibodies Blocking 100 pM of 100 nM Antibody blockinghPD-1-mFc binding 100 pM hPD-1-mFc to hPD-L2-hFc, binding to AntibodyIC₅₀ (M) hPD-L2-hFc, % blocking H4xH9048P2 1.4E−10 98 H2aM7795N2 2.6E−10100 H2aM7798N 1.3E−10 100 H4xH9008P 1.3E−09 94 Isotype control 2 NBI −27Assay theoretical bottom: blocking ELISA with hPD-1-mFc constant andhPD-L2 coat is 5.0E−11 M NBI-non-blocker

As indicated in Table 12, in the first assay format, 23 of the 27anti-PD-1 antibodies blocked 1.5 nM of hPD-1-mFc from binding tohPD-L1-hFc with IC₅₀ values ranging from 190 pM to 3.3 nM with thepercent maximum blockage ranging from 67% to 100%. One antibody,H2aM7796N, was identified as a non-blocker. Three anti-PD-1 antibodies(H4H9068P2, H1M7789N, and H2aM7791N) were identified asnon-blockers/enhancers.

As shown in Table 13, in the second assay format, 23 of the 27 anti-PD-1antibodies blocked 200 pM of biot-hPD-1-hFc from binding to hPD-L1-mFcwith IC₅₀ values ranging from 59 pM to 1.3 nM with maximum percentblockade ranging from 60% to 101%. One antibody, H1M7789N, wasidentified as a non-blocker. Three anti-PD-1 antibodies (H4H9057P2,H4H9068P2, and H2aM7791N) were identified as non-blockers/enhancers.

In the third assay format as shown in Table 14, four anti-PD-1antibodies of the invention, and an Isotype control were tested. All 4anti-PD-1 antibodies of the invention blocked 100 pM (fixedconcentration) of hPD-1-mFc from binding to plate-coated hPD-L2-hFc withIC₅₀ values ranging from 0.13 nM to 1.3 nM and with maximum percentblockade ranging from 94% to 100%.

Example 5: Blocking of PD-1 Binding to PD-L1 as Determined by BiosensorAssay and by Surface Plasmon Resonance

Inhibition of human PD-1 from binding to human PD-L1 by differentanti-PD-1 monoclonal antibodies was studied either using real timebio-layer interferometry assay on an Octet Red96 biosensor instrument(Fortebio Inc.) or using a real-time surface plasmon resonance biosensorassay on a Biacore 3000 instrument.

Inhibition studies for anti-PD-1 monoclonal antibodies expressed with amouse Fc were performed on an Octet Red 96 instrument. First, 100 nM ofa recombinant human PD-1 expressed with a C-terminal mouse IgG2a Fc tag(hPD-1-mFc; SEQ ID NO: 323) was incubated with 500 nM of each anti-PD-1monoclonal antibody for at least 1 hour before running the inhibitionassay. Around 0.8 nm to 1.2 nm of recombinant human PD-L1 expressed witha C-terminal human IgG1 Fc tag (hPD-L1-hFc; SEQ ID NO: 325) was capturedusing anti-human IgG Fc capture Octet biosensor. The Octet biosensorscoated with hPD-L1-hFc were then dipped into wells containing themixture of hPD-1-mFc and different anti-PD-1 monoclonal antibodies. Theentire experiment was performed at 25° C. in Octet HBST buffer (0.01 MHEPES pH7.4, 0.15M NaCl, 3 mM EDTA, 0.05% v/v Surfactant P20, 0.1 mg/mLBSA) with the plate shaking at a speed of 1000 rpm. The biosensors werewashed in Octet HBST buffer in between each step of the experiment. Thereal-time binding responses were monitored during the entire course ofthe experiment and the binding response at the end of every step wasrecorded. Binding of hPD-1-mFc to the captured hPD-L1-hFc was comparedin the presence and absence of different anti-PD-1 monoclonal antibodiesand was used to determine the blocking behavior of the tested antibodiesas shown in Table 15.

TABLE 15 Inhibition of human PD-L1 binding to PD-1 by anti-PD-1monoclonal antibodies expressed with mouse Fc as measured on an OctetRed 96 instrument Binding of the mixture Amount of of 100 nM hPD-L1-hPD-1-mFc and 500 nM Anti-PD-1 hFc Captured anti-PD-1 monoclonal %antibody (nm) antibody (nm) Blocking No Antibody 0.77 0.07 0 H2aM7780N1.07 −0.01 114 H2aM7788N 0.74 0.00 100 H1M7789N 0.80 0.05 29 H2aM7790N0.90 −0.01 114 H2aM7791N 1.17 0.23 −229 H2aM7794N 0.87 −0.01 114H2aM7795N 0.28 −0.01 114 H2aM7796N 0.82 −0.02 129 H2aM7798N 0.85 0.01 86H1M7799N 0.79 0.00 100 H1M7800N 0.96 0.00 100

As shown in Table 15, 9 of the 11 anti-PD-1 antibodies tested on theOctet Red 96 instrument demonstrated strong blocking of hPD-1-mFc frombinding to hPD-L1-hFc ranging from 86% to complete blockade of binding.One anti-PD-1 antibody (H1 M7789N) tested showed weaker blocking ofhPD-1-mFc binding to hPD-L1-hFc with 29% blockade. One antibody(H2aM7791 N) tested demonstrated the ability to enhance the binding ofhPD-1-mFc to hPD-L1-hFc.

Next, inhibition studies for anti-PD-1 monoclonal antibodies expressedwith human Fc were performed on a Biacore 3000 instrument. First, 100 nMof a recombinant human PD-1 expressed with a C-terminal human IgG1 Fctag (hPD-1-hFc; SEQ ID: 324) was incubated with 500 nM of each anti-PD-1monoclonal antibody for at least 2 hours before running the inhibitionassay. A CM5 Biacore sensor surface was first derivatized withpolyclonal rabbit anti-mouse antibody (GE Catalog # BR-1008-38) usingstandard EDC-NHS chemistry. Around 730 RUs of recombinant human PD-L1expressed with a C-terminal mouse IgG2a Fc tag (hPD-L1.mFc; SEQ ID: 326)was then captured followed by the injection of 100 nM of hPD-1.hFc inthe presence and absence of different anti-PD-1 monoclonal antibodies ata flow rate of 25 μL/min for 3 minutes. The entire experiment wasperformed at 25° C. in running buffer comprised of 0.01 M HEPES pH7.4,0.15M NaCl, 3 mM EDTA, 0.05% v/v Surfactant Tween-20 (HBS-ET runningbuffer). The real-time binding responses were monitored during theentire course of the experiment and the binding response at the end ofevery step was recorded. Binding of hPD-1-hFc to the captured hPD-L1-mFcwas compared in the presence and absence of different anti-PD-1monoclonal antibodies and was used to determine the blocking behavior ofthe tested antibodies as shown in Table 16.

TABLE 16 Inhibition of human PD-L1 binding to PD-1 by anti-PD-1monoclonal antibodies expressed with human Fc as measured on a Biacore3000 instrument Binding of the mixture of Anti-PD-1 500 nM of anti- 100nM hPD-1.hFc and monoclonal PD-1 monoclonal 500 nM anti-PD-1 % antibodyantibody (RU) monoclonal antibody (RU) Blocking No Antibody N/A 100 ±1.78 N/A H4H9019P −2 −1 101 H4xH9034P −4 −5 105 H4xH9035P −3 −4 104H4xH9037P −4 −4 104 H4xH9045P −4 −5 105 H4H9048P2 −7 9 91 H4H9057P2 5857 43 H4H9068P2 −2 365 −265 H4xH9119P2 −5 −5 105 H4xH9120P2 1 0 100H4xH9128P2 −5 −5 105 H4xH9135P2 −3 −3 102 H4xH9145P2 −8 −6 106 H4xH8992P3 2 98 H4xH8999P 1 0 100 H4xH9008P 0 1 99 H4H7795N2 −5 −6 106 H4H7798N−6 −6 106 H4H9008P −7 −7 107 H4H9048P2 −4 6 94

As shown in Table 16, 18 out of 20 anti-PD-1 antibodies of the inventiontested on the Biacore 3000 instrument demonstrated strong blocking ofhPD-1-hFc from binding to hPD-L1-mFc with the blockade ranging from 96%to 100%. One antibody demonstrated the ability to enhance the binding ofhPD-1-hFc binding to hPD-L1-mFc. In this study, one of the testedantibodies of the invention (H4H9057P2) demonstrated non-specificbackground binding to the anti-mouse Fc capture surface.

Example 6: Octet Cross-Competition Between Anti-PD-1 Antibodies

Binding competition between anti-PD-1 monoclonal antibodies wasdetermined using a real time, label-free bio-layer interferometry assayon an Octet RED384 biosensor (Pall ForteBio Corp.). The entireexperiment was performed at 25° C. in 0.01 M HEPES pH7.4, 0.15M NaCl, 3mM EDTA, 0.05% v/v Surfactant Tween-20, 0.1 mg/mL BSA (Octet HBS-ETbuffer) with the plate shaking at the speed of 1000 rpm. To assesswhether 2 antibodies were able to compete with one another for bindingto their respective epitopes on a recombinantly expressed human PD-1with a C-terminal myc-myc-hexahistidine tag (hPD-1-MMH; SEQ ID: 321),around 0.1 nM of hPD-1-MMH was first captured onto anti-Penta-Hisantibody coated Octet biosensor tips (Pall ForteBio Corp., #18-5079) bysubmerging the tips for 5 minutes into wells containing a 50 μg/mLsolution of hPD-1-MMH. The antigen captured biosensor tips were thensaturated with the first anti-PD-1 monoclonal antibody (subsequentlyreferred to as mAb-1) by dipping into wells containing 50 μg/mL solutionof mAb-1 for 5 minutes. The biosensor tips were then subsequently dippedinto wells containing a 50 μg/mL solution of a second anti-PD-1monoclonal antibody (subsequently referred to as mAb-2). The biosensortips were washed in Octet HBS-ET buffer in between every step of theexperiment. The real-time binding response was monitored during thecourse of the experiment and the binding response at the end of everystep was recorded. The response of mAb-2 binding to hPD-1-MMHpre-complexed with mAb-1 was compared and competitive/non-competitivebehavior of different anti-PD-1 monoclonal antibodies was determined.Results are summarized in Table 17 (*Self-competing mAb2s are notlisted).

TABLE 17 Cross-competition between pairs of selected anti-PD-1antibodies First antibody applied (“mAb1”) mAb2 Antibodies shown tocompete with mAb1* H4xH8992P H4xH8999P, H1M7799N, H2aM7780N, H1M7800N,H2aM7788N, H2aM7794N, H2aM7798N, H4xH9145P2, H4H9057P2, H4xH9120P2,H4xH9128P2, H4H9019P, H4xH9119P2, H4xH9135P2, H4xH9034P, H2aM7790N,H4xH9035P, H4xH9037P, H4xH9045P, H2aM7795N H4xH8999P H4xH8992P,H1M7799N, H2aM7780N, H1M7800N, H2aM7788N, H2aM7794N, H2aM7798N,H4xH9145P2, H4H9057P2, H4xH9120P2, H4xH9128P2, H4H9019P, H4xH9119P2,H4xH9135P2, H4xH9034P, H2aM7790N, H4xH9035P, H4xH9037P, H4xH9045P,H2aM7795N, H4xH9008P H1M7799N H4xH8992P, H4xH8999P, H2aM7780N, H1M7800N,H2aM7788N, H2aM7794N, H2aM7798N, H4xH9145P2, H4H9057P2, H4xH9120P2,H4xH9128P2, H4H9019P, H4xH9119P2, H4xH9135P2, H4xH9034P, H2aM7790N,H4xH9035P, H4xH9037P, H4xH9045P, H2aM7795N H2aM7780N H4xH8992P,H4xH8999P, H1M7799N, H1M7800N, H2aM7788N, H2aM7794N, H2aM7798N,H4xH9145P2, H4H9057P2, H4xH9120P2, H4xH9128P2, H4H9019P, H4xH9119P2,H4xH9135P2, H4xH9034P, H2aM7790N, H4xH9035P, H4xH9037P, H4xH9045P,H2aM7795N, H4xH9008P H1M7800N H4xH8992P, H4xH8999P, H1M7799N, H2aM7780N,H2aM7788N, H2aM7794N, H2aM7798N, H4xH9145P2, H4H9057P2, H4xH9120P2,H4xH9128P2, H4H9019P, H4xH9119P2, H4xH9135P2, H4xH9034P, H2aM7790N,H4xH9035P, H4xH9037P, H4xH9045P, H2aM7795N, H4xH9008P H2aM7788NH4xH8992P, H4xH8999P, H1M7799N, H2aM7780N, H1M7800N, H2aM7794N,H2aM7798N, H4xH9145P2, H4H9057P2, H4xH9120P2, H4xH9128P2, H4H9019P,H4xH9119P2, H4xH9135P2, H4xH9034P, H2aM7790N, H4xH9035P, H4xH9037P,H4xH9045P, H2aM7795N, H2aM7791N H2aM7794N H4xH8992P, H4xH8999P,H1M7799N, H2aM7780N, H1M7800N, H2aM7788N, H2aM7798N, H4xH9145P2,H4H9057P2, H4xH9120P2, H4xH9128P2, H4H9019P, H4xH9119P2, H4xH9135P2,H4xH9034P, H2aM7790N, H4xH9035P, H4xH9037P, H4xH9045P, H2aM7795N,H4xH9008P H2aM7798N H4xH8992P, H4xH8999P, H1M7799N, H2aM7780N, H1M7800N,H2aM7788N, H2aM7794N, H4xH9145P2, H4H9057P2, H4xH9120P2, H4xH9128P2,H4H9019P, H4xH9119P2, H4xH9135P2, H4xH9034P, H2aM7790N, H4xH9035P,H4xH9037P, H4xH9045P, H2aM7795N, H4xH9008P H4xH9145P2 H4xH8992P,H4xH8999P, H1M7799N, H2aM7780N, H1M7800N, H2aM7788N, H2aM7794N,H2aM7798N, H4H9057P2, H4xH9120P2, H4xH9128P2, H4H9019P, H4xH9119P2,H4xH9135P2, H4xH9034P, H2aM7790N, H4xH9035P, H4xH9037P, H4xH9045P,H4xH9008P H4H9057P2 H4xH8992P, H4xH8999P, H1M7799N, H2aM7780N, H1M7800N,H2aM7788N, H2aM7794N, H2aM7798N, H4xH9145P2, H4xH9120P2, H4xH9128P2,H4H9019P, H4xH9119P2, H4xH9135P2, H4xH9034P, H2aM7790N, H4xH9035P,H4xH9037P, H4xH9045P, H2aM7795N, H2aM7791N, H4xH9048P2 H4xH9120P2H4xH8992P, H4xH8999P, H1M7799N, H2aM7780N, H1M7800N, H2aM7788N,H2aM7794N, H2aM7798N, H4xH9145P2, H4H9057P2, H4xH9128P2, H4H9019P,H4xH9119P2, H4xH9135P2, H4xH9034P, H2aM7790N, H4xH9035P, H4xH9037P,H4xH9045P, H4xH9048P2 H4xH9128P2 H4xH8992P, H4xH8999P, H1M7799N,H2aM7780N, H1M7800N, H2aM7788N, H2aM7794N, H2aM7798N, H4xH9145P2,H4H9057P2, H4xH9120P2, H4H9019P, H4xH9119P2, H4xH9135P2, H4xH9034P,H2aM7790N, H4xH9035P, H4xH9037P, H4xH9045P, H4xH9008P, H4H9066P2,H4xH9048P2 H4H9019P H4xH8992P, H4xH8999P, H1M7799N, H2aM7780N, H1M7800N,H2aM7794N, H2aM7798N, H4xH9145P2, H4H9057P2, H4xH9120P2, H4xH9128P2,H2aM7788N, H4xH9119P2, H4xH9135P2, H4xH9034P, H4xH9035P, H4xH9037P,H4xH9045P, H2aM7795N, H2aM7791N H4xH9119P2 H4xH8992P, H4xH8999P,H1M7799N, H2aM7780N, H1M7800N, H2aM7794N, H2aM7798N, H4xH9145P2,H4H9057P2, H4xH9120P2, H4xH9128P2, H2aM7788N, H4H9019P, H4xH9135P2,H4xH9034P, H4xH9035P, H4xH9037P, H4xH9045P, H2aM7795N, H2aM7791NH4xH9135P2 H4xH8992P, H4xH8999P, H1M7799N, H2aM7780N, H1M7800N,H2aM7794N, H2aM7798N, H4xH9145P2, H4H9057P2, H4xH9120P2, H4xH9128P2,H2aM7788N, H4H9019P, H4xH9119P2, H4xH9034P, H4xH9035P, H4xH9037P,H4xH9045P, H2aM7795N, H2aM7791N H4xH9034P H4xH8992P, H4xH8999P,H1M7799N, H2aM7780N, H1M7800N, H2aM7794N, H2aM7798N, H4xH9145P2,H4H9057P2, H4xH9120P2, H4xH9128P2, H4H9019P, H4xH9119P2, H4xH9135P2,H2aM7788N, H2aM7790N, H4xH9035P, H4xH9037P, H4xH9045P, H2aM7795N,H2aM7791N H2aM7790N H4xH8992P, H1M7799N, H2aM7780N, H1M7800N, H2aM7788N,H2aM7794N, H2aM7798N, H4xH9145P2, H4H9057P2, H4xH9120P2, H4xH9128P2,H4xH9034P, H4xH8999P, H4xH9008P H4xH9035P H4xH8992P, H4xH8999P,H1M7799N, H2aM7780N, H1M7800N, H2aM7794N, H2aM7798N, H4xH9145P2,H4H9057P2, H4xH9120P2, H4xH9128P2, H2aM7788N, H4H9019P, H4XH9119P2,H4xH9034P, H4xH9135P2, H4xH9037P, H4xH9045P, H2aM7795N, H2aM7791NH4xH9037P H4xH8992P, H4xH8999P, H1M7799N, H2aM7780N, H1M7800N,H2aM7794N, H2aM7798N, H4xH9145P2, H4H9057P2, H4xH9120P2, H4xH9128P2,H2aM7788N, H4H9019P, H4xH9119P2, H4xH9034P, H4xH9135P2, H4xH9035P,H4xH9045P, H2aM7795N, H2aM7791N H4xH9045P H4xH8992P, H4xH8999P,H1M7799N, H2aM7780N, H1M7800N, H2aM7794N, H2aM7798N, H4xH9145P2,H4H9057P2, H4xH9120P2, H4xH9128P2, H2aM7788N, H4H9019P, H4xH9119P2,H4xH9034P, H4xH9135P2, H4xH9035P, H4xH9037P, H2aM7795N, H2aM7791NH2aM7795N H4xH8992P, H4xH8999P, H1M7799N, H2aM7780N, H1M7800N,H2aM7794N, H2aM7798N, H4H9057P2, H2aM7788N, H4H9019P, H4xH9119P2,H4xH9034P, H4xH9135P2, H4xH9035P, H4xH9037P, H4xH9045P, H2aM7791NH4xH9008P H4xH8999P, H2aM7780N, H2aM7794N, H2aM7798N, H4xH9145P2,H4xH9128P2, H2aM7790N, H4H9068P2, H1M7799N, H4xH9048P2 H2aM7791NH2aM7788N, H4H9057P2, H4H9019P, H4xH9119P2, H4xH9135P2, H4xH9034P,H4xH9035P, H4xH9037P, H4xH9045P, H2aM7795N H4H9068P2 H4xH9128P2,H4xH9008P, H1M7789N, H4xH9048P2 H1M7789N H4xH9008P, H4H9068P2,H4xH9048P2 H4xH9048P2 H4H9057P2, H4xH9120P2, H4xH9128P2, H4H9019P,H4xH9008P, H4H9068P2, H1M7799N

A second binding competition between a panel of selected anti-PD-1monoclonal antibodies was determined using a real time, label-freebio-layer interferometry assay on an Octet HTX biosensor (Pall ForteBioCorp.). The entire experiment was performed at 25° C. in 0.01 M HEPESpH7.4, 0.15M NaCl, 3 mM EDTA, 0.05% v/v Surfactant Tween-20, 0.1 mg/mLBSA (Octet HBS-ET buffer) with the plate shaking at the speed of 1000rpm. To assess whether 2 antibodies were able to compete with oneanother for binding to their respective epitopes on the hPD-1-MMH,around 0.25 nm of hPD-1-MMH was first captured onto anti-Penta-Hisantibody coated Octet biosensor tips (Fortebio Inc, #18-5079) bysubmerging the tips for 150 seconds into wells containing a 10 μg/mLsolution of hPD-1-MMH. The antigen-captured biosensor tips were thensaturated with a first anti-PD-1 monoclonal antibody (subsequentlyreferred to as mAb-1) by dipping into wells containing 100 μg/mLsolution of mAb-1 for 5 minutes. The biosensor tips were thensubsequently dipped into wells containing a 100 μg/mL solution of secondanti-PD-1 monoclonal antibody (subsequently referred to as mAb-2) for 4minutes. All the biosensors were washed in Octet HBS-ET buffer inbetween every step of the experiment. The real-time binding response wasmonitored during the course of the experiment and the binding responseat the end of every step was recorded as shown in FIG. 2. The responseof mAb-2 binding to hPD-1-MMH pre-complexed with mAb-1 was compared andcompetitive/non-competitive behavior of different anti-PD-1 monoclonalantibodies was determined. Results are summarized in Table 18(*Self-competing mAb2s are not listed).

TABLE 18 Cross-competition between pairs of selected anti-PD-1antibodies First Antibody applied mAb2 Antibodies Shown to (“mAb1”)Compete with mAb1* H4H7795N2 H4H7798N H4H7798N H4H7795N2; H4H9008PH4H9008P H4H7798N; H4H9068P2 H4H9068P2 H4H9008P; H4H9048P2 H4H9048P2H4H9068P2

Under the experimental conditions disclosed in this Example, H4H7795N2cross-competed with H4H7798N; H4H7798N cross-competed with H4H7795N2 andH4H9008P; H4H9008P cross-competed with H4H7798N and H4H9068P2; H4H9068P2cross-competed with H4H9008P and H4H9048P2.

Example 7: Antibody Binding to Cells Overexpressing PD-1

The binding of anti-PD-1 antibodies to a human embryonic kidney cellline (HEK293; ATCC, # CRL-1573) stably transfected with full lengthhuman PD-1 (amino acids 1 to 289 of accession number NP_005009.2)(HEK293/hPD-1) was determined by FACS.

For the assay, adherent cells were detached using trypsin or enzyme-freedissociation buffer and blocked with complete medium. Cells werecentrifuged and resuspended at a concentration of 2.5-6×10{circumflexover ( )}6 cells/mL in cold PBS containing 2% FBS. HEK293 parental andHEK293/hPD-1 cells were then incubated for 15-30 min on ice with 100 nMof each anti-PD-1 antibody. Unbound antibodies were removed by washingwith D-PBS containing 2% FBS, and cells were subsequently incubated withan allophycocyanin-conjugated secondary F(ab′)2 recognizing either humanFc (Jackson ImmunoResearch, #109-136-170) or mouse Fc (JacksonImmunoResearch, #115-136-146) for 15-30 minutes on ice. Cells werewashed with D-PBS containing 2% FBS to remove unbound secondary F(ab′)2and fluorescence measurements were acquired using either a HyperCyte(IntelliCyt, Inc.) flow cytometer or an Accuri flow cytometer (BDBiosciences). Data was analyzed using FlowJo software (Tree Star).

TABLE 19 FACS binding of anti-PD-1 antibodies to HEK293/hPD-1 cells andparental HEK293 cells Ratio of FACS on HEK293 FACS on HEK293/hPD-1parental cells HEK293/hPD- to HEK293 Antibody [MFI] 1 cells [MFI]parental cells H1M7789N 262 24166 92.3 H1M7799N 255 6855 26.9 H1M7800N275 6812 24.7 H2aM7780N 320 23656 73.8 H2aM7788N 305 23112 75.7H2aM7790N 270 47310 175.5 H2aM7791N 274 4948 18.0 H2aM7794N 270 1912771.0 H2aM7795N 288 817 2.8 H2aM7796N 297 49755 167.8 H2aM7798N 300 2344378.1 H4H9019P 111 8610 77.2 H4H9057P2 141 6501 46.1 H4H9068P2 285 19406.8 H4xH8992P 358 17502 48.9 H4xH8999P 809 28875 35.7 H4xH9008P 50926233 51.5 H4xH9034P 147 10115 69.0 H4xH9035P 108 9915 91.7 H4xH9037P108 8787 81.4 H4xH9045P 95 8884 93.7 H4xH9048P2 102 7196 70.8 H4xH9119P2109 9142 84.0 H4xH9120P2 109 9975 91.9 H4xH9128P2 135 9081 67.5H4xH9135P2 114 9380 82.2 H4xH9145P2 226 11552 51.2

As shown in Table 19, 25 of the 27 anti-PD-1 antibodies of the inventionshowed strong binding to the HEK293/hPD-1 cells compared to binding onthe parental HEK293 line. Two antibodies of the invention (H2aM7795N andH4H9068P2) bound weaker to human PD-1 expressing cells compared to theother antibodies tested.

To further characterize anti-PD1 antibodies of the invention,dose-dependent binding to a human embryonic kidney cell line (HEK293;ATCC, # CRL-1573) stably transfected with full length human PD-1 (aminoacids 1 to 289 of accession number NP 005009.2) (HEK293/hPD-1) wasdetermined by FACS.

For the assay, adherent cells were detached using trypsin and blockedwith complete medium. Cells were centrifuged and resuspended at aconcentration of 6×10{circumflex over ( )}6 cells/mL in staining buffer(1% FBS in PBS). To determine the EC₅₀ and E_(max) of the anti-PD1antibodies, 90 uL of cell suspension was incubated for 30 minutes on icewith a serial dilution of anti-PD-1 antibodies and controls diluted to afinal concentration ranging from 5 pM to 100 nM (no mAb sample wasincluded as negative control) in staining buffer. Cells were thencentrifuged and pellets were washed once with staining buffer to removeunbound antibodies. Cells were subsequently incubated for 30 minutes onice either with an allophycocyanin-conjugated secondary F(ab′)2recognizing human Fc (Jackson ImmunoResearch, #109-136-170) or mouse Fc(Jackson ImmunoResearch, #115-136-071). Cells were centrifuged andpellets were washed once with staining buffer to remove unboundsecondary F(ab′)2 and then fixed overnight with a 1:1 dilution ofCytofix (BD Biosciences, #554655) and staining buffer. The followingday, cells were centrifuged and pellets were washed once with stainingbuffer, resuspended and filtered. Fluorescence measurements wereacquired on Hypercyt® cytometer and analyzed in ForeCyt™ (IntelliCyt;Albuquerque, N. Mex.) to determine the mean fluorescence intensities(MFI). The EC₅₀ values were calculated from a four-parameter logisticequation over an 11-point response curve using GraphPad Prism. E_(max)for each antibody was defined as the binding at the highest antibodydose (100 nM) tested.

TABLE 20 Dose dependent FACS binding of anti-PD-1 antibodies toHEK293/hPD-1 cells Max Geom. Mean Antibody EC₅₀ [M] [MFI] @ 100 nMH2aM7779N 2.59E−09 16832 H2aM7780N 1.69E−09 18415 H2aM7781N 5.67E−1013740 H2aM7782N 1.26E−09 17302 H2aM7787N 2.40E−09 15744 H2aM7788N3.21E−10 14827 H2aM7790N 1.71E−10 19196 H2aM7791N No EC₅₀ determined1397 H2aM7794N 1.37E−09 16406 H2aM7795N No EC₅₀ determined 624 H2aM7798N6.985E−11 20900 H1M7799N 3.318E−11 24405 H1M7800N 4.80E−11 20763H4xH8992P 5.45E−11 11368 H4xH8999P 5.27E−11 28341 H4H9019P 1.40E−0929201 H4xH9034P 2.09E−10 32388 H4xH9035P 1.15E−10 28708 H4xH9037P6.74E−10 36441 H4xH9045P 9.17E−11 24662 H4xH9048P2 6.68E−10 33687H4H9057P2 2.363E−10 19953 H4H9068P2 No EC₅₀ determined 639 H4xH9119P23.476E−10 37789 H4xH9120P2 4.797E−10 34057 H4xH9128P2 1.551E−09 37167H4xH9135P2 1.048E−10 32793 H4xH9145P2 2.321E−10 30613 mIgG1 isotype N/A200 mIgG2a isotype N/A 239 hIgG4 isotype N/A 459

TABLE 21 Dose dependent FACS binding of anti-PD-1 antibodies toHEK293/hPD-1 cells Max Geom. Mean Antibody EC₅₀ [M] [MFI] @ 100 nMH4H7795N2 Inconclusive 15188 H4H7798N 5.09E−10 20305 H4H9008PInconclusive 32230 H4H9048P2 1.60E−09 39774 H1M7789N Inconclusive 35574H2aM7796N 4.81E−09 14111 mIgG1 isotype N/A 858 mIgG2a isotype N/A 352hIgG4 isotype N/A 809

As shown in Table 20, 25 of 28 anti-PD1 antibodies of the inventionshowed dose dependent binding to HEK293/hPD-1 cells with EC₅₀ valuesranging from 33.18 pM to 2.59 nM and E_(max) values ranging from 37,789to 11,368 MFI. Three anti-PD1 antibodies of the invention did notdemonstrate strong binding to HEK293/hPD-1 cells and therefore an EC₅₀value could not be determined. None of the isotype controls demonstratedany measurable binding in this assay.

As shown in Table 21, 3 of 6 anti-PD1 antibodies of the invention showeddose dependent binding to HEK293/hPD-1 cells with EC₅₀ values rangingfrom 509 pM to 4.81 nM and E_(max) values ranging from 39,774 to 14,111MFI. Three antibodies of the invention tested bound to HEK293/hPD-1cells, but did not reach a plateau. Therefore their precise EC₅₀ valuescould not be determined and their EC₅₀ values are referred to asinconclusive. None of the isotype controls demonstrated any measurablebinding in this assay.

Example 8: Blocking of PD-1-Induced T-Cell Down-Regulation in aT-Cell/APC Luciferase Reporter Assay

T-cell activation is achieved by stimulating T-cell receptors (TcR) thatrecognize specific peptides presented by major histocompatibilitycomplex class I or II proteins on antigen-presenting cells (APC).Activated TcRs in turn initiate a cascade of signaling events that canbe monitored by reporter genes driven by transcription factors such asactivator-protein 1 (AP-1), Nuclear Factor of Activated T-cells (NFAT)or Nuclear factor kappa-light-chain-enhancer of activated B cells(NFKb). T-cell response is modulated via engagement of co-receptorsexpressed either constitutively or inducibly on T-cells. One suchreceptor is PD-1, a negative regulator of T-cell activity. PD-1interacts with its ligand, PD-L1, which is expressed on target cellsincluding APCs or cancer cells, and acts to deliver inhibitory signalsby recruiting phosphatases to the TcR signalosome, resulting in thesuppression of positive signaling.

The ability of anti-PD-1 antibodies to antagonize PD-1/PD-L1-mediatedsignaling through the PD-1 receptor in human T cell lines was assessedusing an in vitro cell based assay shown in FIG. 1. The bioassay wasdeveloped to measure T cell signaling induced by interaction between APCand T cells by utilizing a mixed culture derived from two mammalian celllines: Jurkat cells (an immortalized T cell line) and Raji cells (a Bcell line). For the first component of the bioassay, Jurkat Clone E6-1cells (ATCC, # T1B-152) were transduced with the Cignal Lenti AP-1 LucReporter (Qiagen-Sabiosciences, # CLS-011L) as per the manufacturer'sinstructions. The lentivirus encodes the firefly luciferase gene underthe control of a minimal CMV promoter, tandem repeats of theTPA-inducible transcriptional response element (TRE) and a puromycinresistance gene. The engineered Jurkat cell line was subsequentlytransduced with a PD-1 chimera comprising the extracellular domain ofhuman PD-1 (amino acids from 1 to 170 of human PD1; accession numberNP_005009.2) and the trans-membrane and cytoplasmic domains of humanCD300a (amino acids from 181 to 299 of human CD300a; accession numberNP_009192.2). The resulting stable cell line(Jurkat/AP1-Luc/hPD1-hCD300a) was selected and maintained in RPMI/10%FBS/penicillin/streptomycin/glutamine supplemented with 500 ug/mL G418+1ug/mL puromycin.

For the second component of the bioassay, Raji cells (ATCC, # CCL-86)were transduced with human PD-L1 gene (amino acids 1-290 of accessionnumber NP_054862.1) that had been cloned into a lentiviral (pLEX) vectorsystem (Thermo Scientific Biosystems, #0H54735). Raji cells, positivefor PD-L1 (Raji/hPD-L1) were isolated by FACS using a PD-L1 antibody andmaintained in lscove/10% FBS/penicillin/streptomycin/glutaminesupplemented with 1 ug/mL puromycin.

To simulate the APC/T cell interaction, a bispecific antibody composedof one Fab arm that binds to CD3 on T cells and the other one Fab armbinding that binds to CD20 on Raji cells (CD3×CD20 bispecific antibody;e.g., as disclosed in US20140088295) was utilized. The presence of thebispecific molecule in the assay results in the activation of the T celland APC by bridging the CD3 subunits on T-cells to CD20 endogenouslyexpressed on Raji cells. Ligation of CD3 with anti-CD3 antibodies hasbeen demonstrated to lead to activation of T cells. In this bioassay,antibodies blocking the PD1/PD-L1 interaction rescue T-cell activity bydisabling the inhibitory signaling and subsequently leading to increasedAP1-Luc activation.

In the luciferase-based bioassay, RPMI1640 supplemented with 10% FBS andpenicillin/streptomycin/glutamine was used as assay medium to preparecell suspensions and antibody dilutions to carry out the screening ofanti-PD1 monoclonal antibodies (mAbs). On the day of the screening, EC50values of anti-PD1 mAbs, in the presence of a fixed concentration ofCD3×CD20 bispecific antibody (30 pM), as well as the EC50 of thebispecific antibody alone, were determined. In the following order,cells and reagents were added to 96 well white, flat-bottom plates. Forthe anti-PD1 mAb EC50 determinations, first a fixed concentration ofCD3×CD20 bispecific antibody (final 30 pM) was prepared and added to themicrotiter plate wells. Then 12-point serial dilutions of anti-PD1 mAbsand controls were added (final concentrations ranging from 1.7 pM to 100nM; plus wells with assay medium alone). For the bispecific antibody(alone) EC₅₀ determination, the bispecific antibody, at finalconcentrations ranging from 0.17 pM to 10 nM (plus wells with assaymedium alone), was added to the microtiter plate wells. Subsequently, a2.5×10{circumflex over ( )}6/mL Raji/hPD-L1 cell suspension was preparedand 20 uL per well was added (final cell number/well 5×10M cells).Plates were left at room temperature (15-20 minutes), while a suspensionof 2.5×10{circumflex over ( )}6/mL ofJurkat/AP1-Luc/hPD1(ecto)-hCD300a(TM-Cyto) was prepared. 20 uL of theJurkat suspension (final cell number/well 5×10{circumflex over ( )}4cells) was added per well. Plates containing the co-culture wereincubated for 5 to 6 hours at 37° C./5% CO₂. Samples were tested induplicates and luciferase activity was then detected after the additionof ONE-Glo™ (Promega, # E6051) reagent and relative light units (RLUs)were measured on a Victor luminometer.

RLU values for each screened antibody were normalized by setting theassay condition with fixed (30 pM) concentration of the CD3/CD20bispecific antibody, but without anti-PD-1 antibody to 100%. Thiscondition corresponds to the maximal AP1-Luc response elicited by thebispecific molecule in the presence of the PD-1/PD-L1 inhibitory signal.Upon addition of the anti-PD-1 antibody, the inhibitory signal issuppressed, and the increased stimulation is shown here as E_(max), thepercentage increase in the signal in the presence of the highestantibody dose tested (100 nM). To compare potency of the anti-PD1antibodies tested, the concentration of antibody at which the normalizedRLU value reached 150% activation was determined from a four-parameterlogistic equation over a 12-point response curve using GraphPad Prism.The results are summarized in Table 22 and Table 23, respectively.

TABLE 22 Anti-PD1 antibody blocking PD-1/PD-L1 dependent inhibition ofAP1-Luc signaling in Experiment 1 Antagonistic assay Concentration (M)of Antagonistic assay Antibody at 150% E_(max) mean [%] @ Antibodyactivation 100 nM Experiment 1 Experiment 1 H4M7789N N/A 135 H4M7799N2.97E−08 183 H4M7800N 1.65E−08 182 H2aM7779N 8.92E−09 214 H2aM7780N6.52E−09 228 H2aM7781N 6.70E−09 230 H2aM7782N 9.96E−09 215 H2aM7787N1.38E−08 215 H2aM7788N 4.72E−09 189 H2aM7790N 5.24E−09 234 H2aM7791N N/A103 H2aM7794N 4.09E−08 170 H2aM7795N N/A 109 H2aM7796N N/A 121 H2aM7798N7.99E−10 239 H4H9019P 1.79E−08 180 H4xH9034P 2.62E−09 202 H4xH9035P1.20E−09 227 H4xH9037P 2.82E−09 195 H4xH9045P 2.23E−08 176 H4xH9048P2N/A 138 H4H9057P2 2.68E−08 212 H4H9068P2 N/A 102 H4xH9119P2 1.11E−08 163H4xH9120P2 1.10E−08 166 H4xH9128P2 3.99E−09 187 H4xH9135P2 1.55E−09 193H4xH9145P2 2.40E−09 185 H4xH8992P 5.32E−09 178 H4xH8999P 8.63E−10 217H4H7798N 1.54E−09 202 mIgG1 isotype control N/A 92 mIgG2a isotypecontrol N/A 91 hIgG4 isotype control N/A 94 N/A = not applicable becauseat the concentrations tested these antibodies did not activate 150%

TABLE 23 Anti-PD1 antibody blocking PD-1/PD-L1 dependent inhibition ofAP1-Luc signaling in Experiment 2 Antagonistic assay Concentration (M)of Antagonistic assay E_(max) Antibody at 150% mean [%] @ 100 nMAntibody activation Experiment 2 Experiment 2 H4H7795N2 N/A 110 H4H7798N1.59E−10 343 H4H9008P 9.84E−08 150 H4H9048P N/A 134 hIgG4 isotypecontrol N/A  98 N/A = not applicable because at the concentrationstested these antibodies did not activate 150%

As shown in Table 22, 25 out of the 31 anti-PD-1 antibodies of theinvention tested blocked PD-1/PD-L1 inhibition with E_(max) valuesranging from 239 to 163. Six out of the 31 anti-PD-1 antibodies of theinvention did not demonstrate substantial blockade of PD1/PD-L1interaction when tested in this assay.

As shown in Table 23, 2 out of the 4 anti-PD-1 antibodies of theinvention tested blocked PD-1/PD-L1 inhibition with E_(max) values of150 and 343%, respectively. 2 out of the 4 anti-PD-1 antibodies of theinvention did not demonstrate substantial blockade of PD1/PD-L1interaction when tested in this assay.

Example 9: In vivo efficacy of anti-PD-1 antibodies

To determine the effect of a select number of anti-PD-1 antibodies ofthe invention in a relevant in vivo model, three MC38.ova tumor growthstudies, involving subcutaneous injection of tumor cells and started ondifferent days, were conducted in mice that were homozygous for theexpression of the extracellular domain of human PD-1 in place ofextracellular domain of mouse PD-1 (PD-1 Humin mice) on a 75%057/B16/25% 129 strain background.

For the studies, mice were divided evenly according to body weight into5 treatment or control groups for Study 1 (5 mice per group), 8treatment or control groups for Study 2 (5 mice per group), and 5treatment or control groups for Study 3 (7 mice per group). At day 0,mice were anesthetized by isoflurane inhalation and then injectedsubcutaneously into the right flank with 5×10⁵ MC38.ova cells insuspension of 100 uL of DMEM for Study 1 or 1×10⁶ MC38.ova cells insuspension of 100 uL of DMEM for Study 2 and Study 3. For Study 1,treatment groups were intraperitoneally injected with 200 ug of eitherone of three anti-PD-1 antibodies of the invention, or an isotypecontrol antibody with irrelevant specificity on days 3, 7, 10, 14, and17 of the experiment, while one group of mice was left untreated. ForStudy 2, treatment groups were intraperitoneally injected with eitherone of three anti-PD-1 antibodies of the invention at 10 mg/kg or 5mg/kg per/dose, one antibody of the invention (H4H7795N2) at 10 mg/kgper dose, or an isotype control antibody with irrelevant specificity at10 mg/kg on days 3, 7, 10, 14, and 17 of the experiment. For Study 3,treatment groups were intraperitoneally injected with either one of twoanti-PD-1 antibodies of the invention at 5 mg/kg or 2.5 mg/kg per/dose,or an isotype control antibody with irrelevant specificity at 5 mg/kg ondays 3, 7, 10, 14, and 17 of the experiment. Experimental dosing andtreatment protocol for groups of mice are shown in Table 24.

TABLE 24 Experimental dosing and treatment protocol for groups of miceDosage amount at each dosage Study # Samples Tested time point Dosinginterval 1 Isotype Control 200 ug Days 3, 7, 10, 14, 17 No treatment N/AN/A H4H7798N 200 ug Days 3, 7, 10, 14, 17 H4H7795N2 200 ug Days 3, 7,10, 14, 17 H4H9008P 200 ug Days 3, 7, 10, 14, 17 2 Isotype Control 10mg/kg Days 3, 7, 10, 14, 17 H4H7795N2 10 mg/kg Days 3, 7, 10, 14, 17H4H7798N 10 mg/kg Days 3, 7, 10, 14, 17 H4H7798N 5 mg/kg Days 3, 7, 10,14, 17 H4H9048P2 10 mg/kg Days 3, 7, 10, 14, 17 H4H9048P2 5 mg/kg Days3, 7, 10, 14, 17 H4H9008P 10 mg/kg Days 3, 7, 10, 14, 17 H4H9008P 5mg/kg Days 3, 7, 10, 14, 17 Isotype Control 5 mg/kg Days 3, 7, 10, 14,17 H4H7798N 5 mg/kg Days 3, 7, 10, 14, 17 3 H4H7798N 2.5 mg/kg Days 3,7, 10, 14, 17 H4H9008P 5 mg/kg Days 3, 7, 10, 14, 17 H4H9008P 2.5 mg/kgDays 3, 7, 10, 14, 17

For the studies, average tumor volumes determined by calipermeasurements and percent survival at Day 14 or 17 and Day 23 or 24 ofeach experiment for each treatment group were recorded. In addition, thenumber of tumor-free mice were also assessed at the end of the study(Day 42 for Study 1 and Day 31 for Study 2 and Study 3). Results,expressed as mean tumor volume (mm³)(±SD), percent survival, and numberof tumor-free mice are shown in Table 23 for Study 1, Table 3 for Study2, and Table 4 for Study 3.

TABLE 25 Mean tumor volume, percent survival and numbers of tumor freemice in each treatment group from in vivo tumor Study 1 Tumor Volume,mm³ Tumor-Free mean (±SD) Survival, % Mice Treatment Day 17 Day 23 Day17 Day 23 Day 42 group 200 200 200 200 200 (n = 5) ug/mouse ug/mouseug/mouse ug/mouse ug/mouse No treatment 189 (±110) 554 (±317) 100% 100%1/5 (20%) Isotype  86 (±114) 515 (±859) 100%  60% 2/5 (40%) controlH4H7798N 0 (0)  0 (0)  100% 100%  5/5 (100%) H4H9008P 14 (±19) 205(±312) 100% 100% 3/5 (60%) H4H7795N2  89 (±176) 445 (±889) 100%  80% 3/5(60%)

As shown in Table 25 for Study 1, mice treated with one antibody of theinvention, H4H7798N did not develop any detectable tumors during thecourse of the study. Mice treated with H4H9008P exhibited a sustainedreduced tumor volume as compared to controls at days 17 and 24 of thestudy with 3 out of 5 mice or 4 out of 5 mice being tumor free by theend of the experiment, respectively. In contrast, treatment with one ofthe anti-PD1 antibodies, H4H7795N2, did not demonstrate significantefficacy in reducing tumor volume in this study as compared to controls.By day 23 of the study, 1 out of 5 mice died in the H4H7795N2 group, and2 out of 5 mice died in the isotype control treatment group. Innon-treatment group and isotype control group some mice exhibitedspontaneous regression of tumors (1 out of 5 mice and 2 out of 5 mice,respectively).

TABLE 26 Mean tumor volume, percent survival and numbers of tumor freemice in each treatment group from in vivo tumor Study 2 Tumor Volume,mm³ Tumor-Free Treatment mean (±SD) Survival, % Mice group Days 17 Day24 Day 17 Day 24 Day 31 (n = 5) 5 mg/kg 10 mg/kg 5 mg/kg 10 mg/kg 5mg/kg 10 mg/kg 5 mg/kg 10 mg/kg 5 mg/kg 10 mg/kg Isotype N/A 449 (±434)N/A 824 (±858) N/A 100% N/A 60% N/A 1/5 (20%) control H4H7798N 17 (±38) 0 (0) 104  0 (0) 100% 100% 100% 100% 4/5 (80%) 5/5/ (±233) (100%)H4H9008P 91 (±204)  12 (±28) 228  96 (±215) 100% 100%  80% 100% 4/5(80%) 4/5 (80%) H4H9048P2 94 (±160)  10 (±21) 328  67 (±150) 100% 100% 80% 100% 3/5 (60%) 4/5 (80%) H4H7795N2 N/A 124 (±209) N/A 359 (±657)N/A 100% N/A  80% N/A 2/5 (40%)

As shown in Table 26 for Study 2, mice treated with one antibody of theinvention, H4H7798N at 10 mg/kg did not develop detectable tumors duringthe course of the study. Groups of mice treated with 10 mg/kg of eitherH4H9008P or H4H9048P2 exhibited substantially reduced tumor volume ascompared to controls at days 17 and 24 of the study. Four out of 5 micein each group treated with 10 mg/kg of either H4H9008P or H4H9048P2 weretumor free at Day 31, whereas in the isotype control treatment grouponly 1 out of 5 animals was tumor free as a result of spontaneous tumorregression. One antibody tested at 10 mg/kg, H4H7795N2, demonstratedsubstantially reduced tumor volume as compared to controls at days 17and 24 of the study, but this antibody was the least efficaciousanti-PD1 antibody with only 2 out of 5 mice surviving at the end of theexperiment.

A dose-dependent response in tumor suppression at the tested doses (5mg/kg and 10 mg/kg) was observed in groups treated with H4H7798N,H4H9008P, and H4H9048P2. H4H7798N or H4H9008P therapy at 5 mg/kg wasless efficacious, with 4 out of 5 tumor-free mice at the end ofexperiment on day 21, whereas 5 out of 5 mice remained tumor-free inboth 10 mg/kg dose groups of H4H7798N, and H4H9008P.

Dunett's test in 2 way ANOVA multiple comparisons revealed that thedifferences in tumor growth between the group treated with isotypecontrol antibody at 10 mg/kg as reference and the groups treated at 10mg/kg with either H4H7798N, H4H9008P, or H4H9048P2 were statisticallysignificant with p value<0.005. The differences in tumor growth betweenthe group treated with isotype control antibody at 10 mg/kg as referenceand the groups treated at 5 mg/kg with either H4H7798N, H4H9008P, orH4H9048P2 were also statistically significant with a p value<0.05.

TABLE 27 Mean tumor volume, percent survival and numbers of tumor freemice in each treatment group from in vivo tumor Study 3 Tumor Volume,mm³ mean (±SD) Survival, % Tumor-Free Mice Treatment Days 14 Day 21 Day14 Day 21 Day 31 group (n = 7) 2.5 mg/kg 5 mg/kg 2.5 mg/kg 5 mg/kg 2.5mg/kg 5 mg/kg 2.5 mg/kg 5 mg/kg 2.5 mg/kg 5 mg/kg Isotype control N/A 94(±44) N/A 405 N/A 100% N/A  86% N/A 0/7 (±326) (0%) H4H7798N  0 (0)  0(0) 19 (±51) 13 (±35) 100% 100% 100% 100% 6/7 6/7 (86%) (86%) H4H9008P41 (±68)  7 (±20) 87 (±123) 16 (±42) 100% 100% 100% 100% 4/7 6/7 (57%)(86%)

As shown in Table 27 for Study 3, 6 out or 7 mice treated with oneantibody of the invention, H4H7798N, or another antibody of theinvention, H4H9008P, at 5 mg/kg were tumor free at the end of theexperiment, whereas there were no tumor free animals in the isotypecontrol group. One tumor-bearing mouse in the IgG4 control group died onpost-implantation day 17. Only 4 out of 7 mice treated with H4H9008P at2.5 mg/kg dose remained tumor free at the end of the experiment. Thedifference in tumor volumes at day 21 between anti-PD-1 antibodiestested and an isotype control group was statistically significant asdetermined by one-way ANOVA with Dunnett's multiple comparison post-testwith p<0.01. All four anti-PD-1 antibodies were equally more efficaciousat the 5 mg/kg dose than at the 2.5 mg/kg dose.

Example 10: Anti-tumor effects of a combination of an anti-PD-1 antibodyand a VEGF antagonist in a mouse early-treatment tumor model

An early-treatment tumor model was developed to test the efficacy of acombination of an anti-PD-1 antibody and a VEGF antagonist. In thismodel, the combination therapy is administered shortly after tumorimplantation. The experiment also used an anti-PD-L1 antibody alone andin combination with the VEGF antagonist. The anti-PD-1 antibody used inthis experiment was anti-mouse PD-1 clone “RPMI-14” with rat IgG2b (BioX Cell, West Lebanon, N.H.). The VEGF antagonist used in this experimentwas aflibercept (a VEGF receptor-based chimeric molecule, also known as“VEGF-trap” or “VEGFR1R2-FcΔC1(a),” a full description of which isprovided elsewhere herein). The anti-PD-L1 antibody used in thisexperiment was an anti-PD-L1 monoclonal antibody with V_(H)/V_(L)sequences of antibody “YW243.55570” according to US20100203056A1(Genentech, Inc.), with mouse IgG2a and which was cross-reactive withmouse PD-L1.

For this experimental model, 1.0×10⁶ Colon-26 tumor cells were implantedsubcutaneously into BALB/c mice at Day 0. Starting on Day 3, prior tothe establishment of measurable tumors, mice were treated with one ofthe mono- or combination therapies, or control combination, as set forthin Table 28.

TABLE 28 Experimental dosing and treatment groups Treatment Group FirstAgent Second Agent Control Combination IgG2a isotype control hFc control(250 μg, IP) (250 μg, SC) VEGF Trap only IgG2a isotype controlAflibercept (250 μg, IP) (10 mg/kg, SC) anti-PD-1 only anti-PD-1 mAbRPMI-14 hFc control (250 μg, IP) (250 μg, SC) anti-PD-L1 only anti-PD-L1mAb hFc control (250 μg, IP) (250 μg, SC) VEGF Trap + anti-PD-1 mAbRPMI-14 Aflibercept anti-PD-1 (250 μg, IP) (10 mg/kg, SC) VEGF Trap +anti-PD-L1 mAb Aflibercept anti-PD-L1 (250 μg, IP) (10 mg/kg, SC)

The various therapies were administered at five different time pointsover a two week period (i.e., injections at Day 3, Day 6, Day 10, Day 13and Day 19).

Animals in each therapy group were evaluated in terms of tumorincidence, tumor volume, median survival time, and number of tumor-freeanimals at Day 50. The extent of tumor growth is summarized in FIG. 2(tumor growth curves) and FIG. 3 (tumor volume at Day 28). Results arealso summarized in Table 29.

TABLE 29 Tumor-free mice in treatment groups Treatment Group No. ofTumor-Free Animals by Day 50 Control Combination 0/10 VEGF Trap only3/10 anti-PD-1 only 4/10 anti-PD-L1 only 5/10 VEGF Trap + anti-PD-1 7/10VEGF Trap + anti-PD-L1 9/10

Tumor growth was substantially reduced in animals treated with thecombination of VEGF Trap+anti-PD-1 antibody as compared with treatmentregimens involving either therapeutic agent alone (see FIGS. 2 and 3).Furthermore, survival was substantially increased in the VEGFTrap+anti-PD-1 antibody group, with 70% of animals surviving to at leastday 50 after tumor implantation. By contrast, for the anti-PD-1 and VEGFTrap monotherapy groups, survival to Day 50 was only 40% and 30%respectively (see FIG. 3 and Table 29).

Example 11: Clinical trial study of repeat dosing with anti-PD-1antibody as single

therapy and in combination with other anti-cancer therapies in patientswith advanced malignancies

This is a dose-escalation study of anti-PD-1 antibody, alone or incombination with radiation therapy, cyclophosphamide, or both inpatients with advanced malignancies. The exemplary anti-PD-1 antibody(“mAb”) used in this Example comprises HCVR of SEQ ID NO: 162 and LCVRof SEQ ID NO: 170.

Study Objectives

The primary objective of the study is to characterize the safety,tolerability, DLTs of mAb administered IV as monotherapy, or incombination with targeted radiation (with the intent to have this serveas an immuno-stimulatory, rather than primarily tumor-ablative therapy),low-dose cyclophosphamide (a therapy shown to inhibit regulatory T-cellresponses), or both in patients with advanced malignancies.

The secondary objectives of the study are: (1) to determine arecommended phase 2 dose (RP2D) of mAb as monotherapy and in combinationwith other anti-cancer therapies (targeted radiation, low-dosecyclophosphamide, or both); (2) to describe preliminary antitumoractivity of mAb, alone and with each combination partner (s); (3) tocharacterize the PK of mAb as monotherapy and in combination with otheranti-cancer therapies (targeted radiation, low-dose cyclophosphamide, orboth); and (4) to assess immunogenicity of mAb.

Study Design

Safety will be assessed in separate, standard 3+3 dose escalationcohorts (in monotherapy, combination with radiation therapy, combinationwith cyclophosphamide, and combination with radiation therapy pluscyclophosphamide). The choice of combination therapy with radiation,cyclophosphamide, or both will be based on investigator assessment ofthe best choice of therapy for an individual patient in consultationwith the sponsor. To be enrolled in a radiotherapy cohort, a patientmust have a lesion that can be safely irradiated and for which radiationat the limited, palliative doses contemplated would be consideredmedically appropriate, and at least one other lesion suitable forresponse evaluation. A patient will be allowed to enroll only if a slotis available in the cohort for the chosen treatment.

Patients will undergo screening procedures to determine eligibilitywithin 28 days prior to the initial administration of mAb. Followingenrollment of patients into a mAb monotherapy cohort, enrollment ofsubsequent cohorts will be determined by occurrence of DLTs in priorcohorts (i.e., no DLT in a cohort of 3 patients, or no more than 1 DLTin an expanded cohort of 6 patients), and the availability of patientslots. The planned monotherapy dose levels are 1, 3, or 10 mg/kgadministered IV every 14 days (2 weeks).

Once one or both of the 1 mg/kg or 3 mg/kg mAb monotherapy cohort DLTobservation periods are completed without a DLT in a cohort of 3patients or with no more than 1 DLT in an expanded cohort of 6 patients,patients can be enrolled into a cohort combining cyclophosphamide orradiotherapy with mAb at that monotherapy dose level. Patients can beenrolled into a combination mAb+cyclophosphamide/radiotherapy cohortonce the DLT observation periods for both the cohort for that mAb doselevel+cyclophosphamide and the cohort for that mAb dose level+the sameradiotherapy regimen are completed with no DLT in a cohort of 3patients, or no more than 1 DLT in an expanded cohort of 6 patients.

Once the 3 mg/kg mAb monotherapy cohort DLT observation period iscompleted with no DLT in a cohort of 3 patients, or no more than 1 DLTin an expanded cohort of 6 patients, a 10 mg/kg mAb monotherapy cohortmay also enroll.

mAb 3 mg/kg and 10 mg/kg monotherapy cohorts will enroll only after therequisite number of patients in the prior monotherapy dose cohort (ie, 1mg/kg and 3 mg/kg, respectively) have cleared the 28 day DLT observationperiod without a maximum tolerated dose (MTD) being demonstrated forthat dose level. A mAb 1 mg/kg combination treatment cohort will enrollonly after completion of the DLT observation period for the 1 mg/kgmonotherapy cohort. Combination cohorts receiving 3 mg/kg mAb willenroll only when the requisite number of patients in the respective 1mg/kg mAb combination cohorts has cleared the DLT observation periodwithout demonstrating a MTD. Triple combination cohorts combining mAbwith cyclophosphamide and a radiation regimen will enroll only when therequisite number of patients in both corresponding double combinationcohorts at that dosage level have cleared the DLT observation periodwithout a MTD being demonstrated.

Table 30 summarizes the dose-escalation cohorts in which patients willbe enrolled.

TABLE 30 Possible Dose-escalation Cohorts n Possible Assigned TreatmentCohort 3-6 0.3 mg/kg mAb monotherapy (to be enrolled only if MTD < 1mg/kg mAb) 3-6   1 mg/kg mAb monotherapy 3-6   3 mg/kg mAbmonotherapy^(a)) 3-6  10 mg/kg mAb monotherapy^(b)) 3-6   1 mg/kg^(a))mAb + radiotherapy (6 Gy × 5) 3-6   1 mg/kg^(a)) mAb + radiotherapy (9Gy × 3) 3-6   3 mg/kg^(b)) (or MTD) mAb + cyclophosphamide 3-6   3mg/kg^(b)) (or MTD) mAb + radiotherapy (6 Gy × 5) 3-6   3 mg/kg^(b)) (orMTD) mAb + radiotherapy (9 Gy × 3) 3-6   3 mg/kg^(b)) (or MTD) mAb +radiotherapy (6 Gy × 5) + cyclophosphamide 3-6   3 mg/kg^(b)) (or MTD)mAb + radiotherapy (9 Gy + 3) + cyclophosphamide

A DLT is defined as any of the following: a non-hematologic toxicity(e.g., uveitis, or any other irAE), or a hematologic toxicity (e.g.,neutropenia, thrombocytopenia, febrile neutropenia).

The maximum tolerated dose (MTD) is defined as the highest dose at whichfewer than a third of an expanded cohort of 6 patients experience a DLTduring the first cycle of treatment. Thus, the MTD is defined as thedose level immediately below the level at which dosing is stopped due tothe occurrence of 2 or more DLTs in an expanded cohort of 6 patients. Ifdose escalation is not stopped due to the occurrence of DLTs, it will beconsidered that the MTD has not been determined. It is possible that anMTD may not be defined in this study, either for a monotherapy group orfor individual combination groups. Additionally, it is possible that mAbMTDs may differ between monotherapy and each combination treatmentregimen.

Study Duration

Patients will receive up to 48 weeks of treatment, after which therewill be a 24 week follow-up period. A patient will receive treatmentuntil the 48 week treatment period is complete, or until diseaseprogression, unacceptable toxicity, withdrawal of consent, or meeting ofanother study withdrawal criterion. After a minimum of 24 weeks oftreatment, patients with confirmed complete responses (CR) may elect todiscontinue treatment and continue with all relevant study assessments(eg, efficacy assessments). After a minimum of 24 weeks of treatment,patients with tumor burden assessments of stable disease (SD) or partialresponse (PR) that have been unchanged for 3 successive tumorevaluations may also elect to discontinue treatment and continue withall relevant study assessments (e.g., efficacy assessments).

Study Population

The target population for this study comprises patients with advancedmalignancies who are not candidates for standard therapy, unwilling toundergo standard therapy, or for whom no available therapy is expectedto convey clinical benefit; and patients with malignancies that areincurable and have failed to respond to or showed tumor progressiondespite standard therapy.

Inclusion criteria: A patient must meet with the following criteria tobe eligible for inclusion in the study: (1) demonstrated progression ofa solid tumor with no alternative standard-of-care therapeutic optionavailable; (2) at least 1 lesion for response assessment. Patientsassigned to radiotherapy require at least one additional lesion that canbe safely irradiated while sparing the index lesions and for whichradiation at the limited, palliative doses contemplated would beconsidered medically appropriate; (3) Eastern Cooperative Oncology Group(ECOG) performance status 1; (4) more than 18 years old; (5) hepaticfunction: a. total bilirubin 1.5× upper limit of normal (ULN; if livermetastases 3×ULN), b. transaminases 3×ULN (or 5.0×ULN, if livermetastases), c. alkaline phosphatase (ALP) 2.5×ULN (or 5.0×ULN, if livermetastases); (6) renal function: serum creatinine 1.5×ULN; (7)neutrophil count (ANC) 1.5×10⁹/L, c. platelet count 75×10⁹/L; (8)ability to provide signed informed consent; and (9) ability andwillingness to comply with scheduled visits, treatment plans, laboratorytests, and other study-related procedures.

Exclusion criteria: A patient who meets any of the following criteriawill be excluded from the study: (1) Ongoing or recent (within 5 years)evidence of significant autoimmune disease that required treatment withsystemic immunosuppressive treatments, which may suggest risk for irAEs;(2) Prior treatment with an agent that blocks the PD-1/PD-L1 pathway;(3) Prior treatment with other immune modulating agents within fewerthan 4 weeks or 4 half-lives, whichever is greater, prior to the firstdose of mAb; (4) Examples of immune modulating agents include blockersof CTLA-4, 4-1 BB (CD137), OX-40, therapeutic vaccines, or cytokinetreatments; (5) Untreated brain metastasis (es) that may be consideredactive. Patients with previously treated brain metastases mayparticipate provided they are stable (ie, without evidence ofprogression by imaging for at least 4 weeks prior to the first dose ofstudy treatment, and any neurologic symptoms have returned to baseline),and there is no evidence of new or enlarging brain metastases; (6)Immunosuppressive corticosteroid doses (>10 mg prednisone daily orequivalent) within 4 weeks prior to the first dose of mAb; (7) Deep veinthrombosis, pulmonary embolism (including asymptomatic pulmonaryembolism identified on imaging), or other thromboembolic event withinthe 6 months preceding the first dose of mAb; (8) Active infectionrequiring therapy, including known infection with human immunodeficiencyvirus, or active infection with hepatitis B or hepatitis C virus; (9)History of pneumonitis within the last 5 years; (10) Any investigationalor antitumor treatment within 30 days prior to the initialadministration of mAb; (11) History of documented allergic reactions oracute hypersensitivity reaction attributed to treatment with antibodytherapies in general, or to agents specifically used in the study; (12)Known allergy to doxycycline or tetracycline (precaution due to presenceof trace components in mAb); (13) Breast-feeding; (14) Positive serumpregnancy test; (15) History within the last 5 years of an invasivemalignancy other than the one treated in this study, with the exceptionof resected/ablated basal or squamous-cell carcinoma of the skin orcarcinoma in situ of the cervix, or other local tumors considered curedby local treatment; (16) Acute or chronic psychiatric problems that,under the evaluation of the investigator, make the patient ineligiblefor participation; and (17) Continued sexual activity in men or women ofchildbearing potential who are unwilling to practice adequatecontraception during the study. Study Treatments

mAb will be supplied as a liquid in sterile, single-use vials. Each vialwill contain a volume sufficient to withdraw 10 mL of mAb at aconcentration of 25 mg/mL. Instructions on dose preparation are providedin the study reference manuals. mAb will be administered in anoutpatient setting as a 30 minute IV infusion. Each patient's dose willdepend on individual body weight. The dose of mAb must be adjusted eachcycle for changes in body weight of 0%. mAb will be administered aloneand in combination with radiation and or cyclophosphamide. Monotherapy

mAb will be administered in an outpatient setting by IV infusion over 30minutes every 14 days for 48 weeks (ie, Days 1, 15±3, 29±3, and 43±3 ofa 56 day cycle). Planned monotherapy regimens to be assigned mayinclude: (i) 1 mg/kg IV infusion over 30 minutes every 14 days for 48weeks; (ii) 3 mg/kg infusion over 30 minutes every 14 days for 48 weeks;(iii) 10 mg/kg infusion over 30 minutes every 14 days for 48 weeks; and(iv) 0.3 mg/kg infusion over 30 minutes every 14 days for 48 weeks (ifMTD is determined to be below 1 mg/kg). Combination Therapy

Concomitant radiation therapy and cyclophosphamide will be suppliedthrough a prescription and their usage, dose, dose modifications,reductions, or delays, as well as any potential AEs resulting from theiruse, will be tracked along with that of mAb.

Co-administration of mAb and radiation: mAb will be administered by IVinfusion over 30 minutes every 14 days for 48 weeks in combination withradiation treatment from day 8 to day 12. Planned combination mAb andradiation therapy regimens may include:

-   -   1 mg/kg mAb infusion over 30 minutes every 14 days for 48 weeks        plus 30 Gy radiotherapy (6 Gy×5 times/week; given 1 week after        the first dose of mAb, preferably on consecutive days)    -   1 mg/kg mAb infusion over 30 minutes every 14 days for 48 weeks        plus 27 Gy radiotherapy (9 Gy×3 times/week; given 1 week after        the first dose of mAb, preferably not on consecutive days)    -   3 mg/kg mAb infusion over 30 minutes every 14 days for 48 weeks        plus 30 Gy radiotherapy (6 Gy×5 times/week; given 1 week after        the first dose of mAb, preferably on consecutive days)    -   3 mg/kg mAb infusion over 30 minutes every 14 days for 48 weeks        plus 27 Gy radiotherapy (9 Gy×3 times/week; given 1 week after        the first dose of mAb, preferably not on consecutive days)

Patients will receive either 30 Gy given as 5 fractions of 6 Gyadministered daily starting 1 week after the first dose of mAb, or 27 Gygiven as 3 fractions of 9 Gy administered every other day starting 1week after the first dose of mAb. The lesion selected for radiationshould be a lesion that can be safely irradiated with focal irradiationwhile sparing the index lesion(s), and for which radiation at thelimited, palliative doses contemplated would be considered medicallyappropriate. The target dose for a patient will be based on cohortassignment and should conform to the normal tissue requirements, inaccord with standard radiation oncology practice. Treatment at theprotocol-specified dosing regimen is permitted only if the normal tissuecriteria are met. If the normal tissue criteria cannot be met at eitherof the radiation therapy regiments specified in the protocol, thepatient is not eligible for enrollment in a combination radiationtreatment cohort in this study.

Co-administration of mAb and cyclophosphamide: mAb will be administeredby IV infusion over 30 minutes every 14 days (2 weeks) for 48 weeks incombination with cyclophosphamide 200 mg/m² every 14 days for 4 doses.Each of the 4 cyclophosphamide doses will be administered 1 day beforeeach of the first 4 mAb doses (days −1, 14, 28, and 42 of the first 56day cycle).

Though cyclophosphamide has been used successfully concurrently withother drugs, the rate of metabolism and the leukopenic activity ofcyclophosphamide reportedly are increased by chronic administration ofhigh doses of phenobarbital. Cyclophosphamide treatment causes a markedand persistent inhibition of cholinesterase activity, thus potentiatingthe effect of succinylcholine chloride. The planned combination mAb andcyclophosphamide regimen to be assigned is:

-   -   Cyclophosphamide 200 mg/m² every 14 days (days −1, 14, 28, and        42 of the first 56 day cycle) for a total of 4 doses plus    -   3 mg/kg mAb infusion over 30 minutes every 14 days for 48 weeks        (provided monotherapy dose of 3 mg/kg<MTD; if 3 mg/kg>MTD, dose        will be 1 mg/kg).

Co-administration of mAb, radiation and cyclophosphamide: The plannedcombination mAb, radiation, and cyclophosphamide regimen includes:

-   -   Cyclophosphamide 200 mg/m² every 14 days (days −1, 14, 28, and        42 of the first 56 day cycle) for a total of 4 doses plus    -   27 Gy radiotherapy (9 Gy×3 times/week; given 1 week after the        first dose of mAb, preferably not on consecutive days) OR 30 Gy        radiotherapy (6 Gy×5 times/week; given 1 week after the first        dose of mAb, preferably on consecutive days) plus    -   3 mg/kg mAb infusion over 30 minutes every 14 days for 48 weeks        (provided monotherapy dose of 3 mg/kg<MTD; if 3 mg/kg>MTD, dose        will be 1 mg/kg)

Study Variables

Primary Variables: Primary safety variables include incidence of DLTs,incidence and severity of treatment-emergent adverse events (TEAEs), andabnormal laboratory findings through 48 weeks of treatment.

Secondary Variables: Key secondary variables include the following:

-   -   Serum concentration and pharmacokinetics (PK) of mAb    -   Antitumor activities assessed using the appropriate criteria for        the indication:        -   Response Evaluation Criteria in Solid Tumors (RECIST)            criteria measured by computed tomography (CT) or magnetic            resonance imaging (MRI)        -   o Other assessment criteria should also be used for specific            tumors in which RECIST measurements are not the standard.        -   Immune-Related Response Criteria (irRC) applied to RECIST            measurements.

In all cases, irRC will be the governing tool to determine progressionof disease (PD), SD, CR, or PR. Standard RECIST data will also becollected for information purposes.

-   -   Anti-mAb antibodies

Study Procedures

The following procedures will be performed at screening for the purposeof determining study eligibility or characterizing the baselinepopulation: (i) serum 6-HOG (result must be 72 hours before first dose);(ii) Collection of archived tumor material: After a patient has giveninformed consent, the patient will be asked to arrange to provide anyavailable previously collected tumor samples; (iii) Brain MRI: Brain MRIis required at screening if not performed in the prior 60 days; and (iv)Chest x-ray: Chest is x-ray required at screening if not performed inthe prior 60 days.

Efficacy Procedures: A CT or MRI for tumor assessment will be performedat the screening visit (within 28 days prior to infusion) and duringevery cycle (approximately every 8 weeks) on day 56±3, and when diseaseprogression is suspected. Additionally, for patients who have notprogressed on study, tumor assessment will be performed for follow-upvisits 3, 5, and 7. Once the choice has been made to use CT scan or MRI,subsequent assessments will be made using the same modality.

Tumor response evaluation will be performed according to immune-relatedresponse criteria (irRC; Nishino 2013). Assessments according toResponse Evaluation Criteria in Solid Tumors (RECIST) version 1.1(Eisenhauer 2009) will also be performed as a supportive exploration;however, the primary determination of disease progression for anindividual patient will be made according to irRC. Measurable lesionsselected as target lesions for RECIST assessments will also be includedas index lesions for irRC assessments.

Safety Procedures: Vital signs, including temperature, resting bloodpressure, pulse, and respiration, will be collected. When scheduled atthe same visit as other procedures, vital signs should be measured priorto clinical laboratory assessments, PK, or exploratory samplecollection. During cycle 1, vital signs will be recorded on treatmentdays prior to treatment, at the end of the infusion, every 30 minutesfor the first 4 hours post-infusion, and at 6 and 8 hours post studydrug administration. On subsequent cycles, vital signs on treatment dayswill be assessed and documented prior to the infusion, every 30 minutesfor the first 2 hours, and then hourly until 4 hours following studydrug administration.

A thorough complete or limited physical examination will be performed atvisits. Complete physical examination will include examination of skin,head, eyes, nose, throat, neck, joints, lungs, heart, pulse, abdomen(including liver and spleen), lymph nodes, and extremities, as well as abrief neurologic examination. Limited physical examination will includelungs, heart, abdomen, and skin.

A standard 12-lead ECG will be performed. Any ECG finding that is judgedby the investigator as a clinically significant change (worsening)compared to the baseline value will be considered an AE, recorded, andmonitored.

Immune safety assays consist of rheumatoid factor (RF), thyroidstimulating hormone (TSH), C-reactive protein (CRP), and antinuclearantibody (ANA) titer and pattern. If, during the course of the study, a4-fold or greater increase from baseline in RF or ANA or abnormal levelsof TSH or CRP are observed, the following tests may also be performed:anti-DNA antibody, anti-Sjögren's syndrome A antigen (SSA) antibody(Ro), anti-Sjögren's syndrome B antigen (SSB) antibody (La),antithyroglobulin antibody, anti-LKM antibody, antiphospholipidantibody, anti-islet cell antibody, antineutrophil cytoplasm antibody,C3, C4, CH50. Activated partial thromboplastin time (aPTT) andInternational Normalized Ratio (INR) will be analyzed by the site'slocal laboratory.

Safety

An adverse event (AE) is any untoward medical occurrence in a patientadministered a study drug which may or may not have a causalrelationship with the study drug. Therefore, an AE is any unfavorableand unintended sign (including abnormal laboratory finding), symptom, ordisease which is temporally associated with the use of a study drug,whether or not considered related to the study drug. An AE also includesany worsening (ie, any clinically significant change in frequency and/orintensity) of a pre-existing condition that is temporally associatedwith the use of the study drug. Progression of underlying malignancywill not be considered an AE if it is clearly consistent with thetypical progression pattern of the underlying cancer (including timecourse, affected organs, etc.). Clinical symptoms of progression may bereported as AEs if the symptom cannot be determined as exclusively dueto the progression of the underlying malignancy, or does not fit theexpected pattern of progression for the disease under study.

An serious adverse event (SAE) is any untoward medical occurrence thatat any dose results in death, is life-threatening, requires in-patienthospitalization or prolongation of existing hospitalization, results inpersistent or significant disability/incapacity (substantial disruptionof one's ability to conduct normal life functions), is a congenitalanomaly/birth defect.

Patient information on all AEs and SAEs will be recorded.

Statistical Plan

The study dose escalation is based on a traditional 3+3 design with 3 to6 patients assigned per dose level. The exact number of patientsenrolled in the study will depend on the number of protocol-defined DLTsobserved, and the need to expand currently defined dose levels, or openadditional cohorts at lower dose levels. After the required initialenrollment to the next cohort in the dose escalation has occurred,enrollment to each of the previous cohorts below the MTD for thattreatment will be expanded (if not previously expanded duringescalation) to a total of 6 patients.

Data will be summarized using descriptive statistics only. In general,data will be summarized by dose levels and combinations. The safetysummaries and analyses will be performed on the safety analysis set(SAF). The primary analysis of safety will be based ontreatment-emergent AEs (TEAEs).

The present invention is not to be limited in scope by the specificembodiments described herein. Indeed, various modifications of theinvention in addition to those described herein will become apparent tothose skilled in the art from the foregoing description and theaccompanying figures. Such modifications are intended to fall within thescope of the appended claims.

What is claimed is:
 1. An isolated antibody or antigen-binding fragment thereof that competes for binding to human programmed death-1 (PD-1) protein with a reference antibody or antigen-binding fragment thereof comprising the complementarity determining regions (CDRs) of a heavy chain variable region (HCVR), wherein the HCVR has an amino acid sequence selected from the group consisting of HCVR sequences listed in Table 1; and the CDRs of a light chain variable region (LCVR), wherein the LCVR has an amino acid sequence selected from the group consisting of LCVR sequences listed in Table 1, and wherein the antibody has one or more of the following properties: (a) blocks human PD-1 protein binding to PD-L1 with an IC₅₀ of less than 3 nM as measured in a competition sandwich ELISA assay at 25° C.; (b) binds monomeric human PD-1 with a binding dissociation equilibrium constant (K_(D)) of less than about 50 nM as measured in a surface plasmon resonance assay at 37° C.; (c) binds monomeric human PD-1 with a K_(D) less than about 12 nM in a surface plasmon resonance assay at 25° C.; (d) binds monomeric cynomolgus PD-1 with a K_(D) less than about 8.5 nM in a surface plasmon resonance assay at 25° C.; (e) binds monomeric human PD-1 with a dissociative half-life (t½) of greater than about 6.3 minutes as measured in a surface plasmon resonance assay at 25° C.; and (f) binds monomeric human PD-1 with a dissociative half-life (t½) of greater than about 0.9 minutes as measured in a surface plasmon resonance assay at 37° C.
 2. The isolated antibody or antigen-binding fragment of claim 1, wherein the reference antibody or antigen-binding fragment thereof comprises an HCVR/LCVR amino acid sequence pair as set forth in Table
 1. 3. The isolated antibody or antigen-binding fragment of claim 2, wherein the reference antibody comprises an HCVR/LCVR amino acid sequence pair selected from the group consisting of SEQ ID NOs: 130/138, 162/170, 234/202, and 314/186.
 4. An isolated human monoclonal antibody or antigen-binding fragment thereof that binds specifically to human PD-1, wherein the antibody or antigen-binding fragment thereof comprises three heavy chain CDRs (HCDR1, HCDR2 and HCDR3) contained within any one of the HCVR sequences listed in Table 1; and three light chain CDRs (LCDR1, LCDR2 and LCDR3) contained within any one of the LCVR sequences listed in Table
 1. 5. The isolated antibody or antigen-binding fragment thereof of claim 4, comprising a HCVR having an amino acid sequence selected from the group consisting of HCVR sequences listed in Table
 1. 6. The isolated antibody or antigen-binding fragment thereof of either claim 4 or 5, comprising a LCVR having an amino acid sequence selected from the group consisting of LCVR sequences listed in Table
 1. 7. The isolated antibody or antigen-binding fragment thereof of any one of claims 4-6, comprising: (a) a HCVR having an amino acid sequence selected from the group consisting of HCVR sequences listed in Table 1; and (b) a LCVR having an amino acid sequence selected from the group consisting of LCVR sequences listed in Table
 1. 8. The isolated antibody or antigen-binding fragment thereof of any one of claims 1-7, comprising: (a) a HCDR1 domain having an amino acid sequence selected from the group consisting of SEQ ID NOs: 4, 20, 36, 52, 68, 84, 100, 116, 132, 148, 164, 180, 196, 212, 220, 228, 236, 244, 252, 260, 268, 276, 284, 292, 300, 308, and 316; (b) a HCDR2 domain having an amino acid sequence selected from the group consisting of SEQ ID NOs: 6, 22, 38, 54, 70, 86, 102, 118, 134, 150, 166, 182, 198, 214, 222, 230, 238, 246, 254, 262, 270, 278, 286, 294, 302, 310, and 318; (c) a HCDR3 domain having an amino acid sequence selected from the group consisting of SEQ ID NOs: 8, 24, 40, 56, 72, 88, 104, 120, 136, 152, 168, 184, 200, 216, 224, 232, 240, 248, 256, 264, 272, 280, 288, 296, 304, 312, and 320; (d) a LCDR1 domain having an amino acid sequence selected from the group consisting of SEQ ID NOs: 12, 28, 44, 60, 76, 92, 108, 124, 140, 156, 172, 188, and 204; (e) a LCDR2 domain having an amino acid sequence selected from the group consisting of SEQ ID NOs: 14, 30, 46, 62, 78, 94, 110, 126, 142, 158, 174, 190, and 206; and (f) a LCDR3 domain having an amino acid sequence selected from the group consisting of SEQ ID NOs: 16, 32, 48, 64, 80, 96, 112, 128, 144, 160, 176, 192, and
 208. 9. An isolated antibody or antigen-binding fragment thereof that blocks PD-1 binding to PD-L1 comprising the CDRs of a HCVR, wherein the HCVR has an amino acid sequence selected from the group consisting of SEQ ID NOs: 18, 34, 50, 66, 82, 114, 130, 162, 178, 194, 210, 218, 226, 234, 242, 258, 266, 274, 282, 290, 298, 306 and 314; and the CDRs of a LCVR, wherein the LCVR has an amino acid sequence selected from the group consisting of SEQ ID NOs: 26, 42, 58, 74, 90, 122, 138, 170, 186, and
 202. 10. The isolated antibody or antigen-binding fragment of claim 9, comprising a HCVR/LCVR amino acid sequence pair selected from the group consisting of SEQ ID NOs: 130/138, 162/170, 234/202, and 314/186.
 11. An isolated antibody or antigen-binding fragment thereof that binds human PD-1, wherein the antibody or antigen-binding fragment thereof enhances PD-1 binding to PD-L1, as measured by a competition sandwich ELISA assay at 25° C.
 12. The isolated antibody or antigen-binding fragment thereof of claim 11, wherein the antibody comprises the CDRs of a HCVR, wherein the HCVR has an amino acid sequence selected from the group consisting of SEQ ID NOs: 2, 98, and 250; and the CDRs of a LCVR, wherein the LCVR has an amino acid sequence selected from the group consisting of SEQ ID NOs: 10, 106, and
 202. 13. The isolated antibody or antigen-binding fragment thereof of claim 12, wherein the antibody comprises an HCVR/LCVR amino acid sequence pair selected from the group consisting of SEQ ID NOs: 2/10, 98/106, and 250/202.
 14. The antibody or antigen-binding fragment thereof of any one of claims 1-13, wherein the antibody is a multi-specific antigen-binding molecule.
 15. A pharmaceutical composition comprising an isolated antibody or antigen-binding fragment thereof that binds to PD-1 according to any one of claims 1-14 and a pharmaceutically acceptable carrier or diluent.
 16. An isolated polynucleotide molecule comprising a polynucleotide sequence that encodes a HCVR of an antibody as set forth in any one of claims 1-13.
 17. An isolated polynucleotide molecule comprising a polynucleotide sequence that encodes a LCVR of an antibody as set forth in any one of claims 1-13.
 18. A vector comprising the polynucleotide sequence of claim 16 or
 17. 19. A cell expressing the vector of claim
 18. 20. A multi-specific antigen-binding molecule or antigen-binding fragment thereof comprising a first antigen-binding specificity that binds specifically to PD-1 and a second antigen-binding specificity that comprises an extracellular domain of PD-L1 or PD-L2, or fragment thereof.
 21. A multi-specific antigen-binding molecule or antigen-binding fragment thereof comprising a first antigen-binding specificity that binds specifically to PD-1 and a second antigen-binding specificity that binds specifically to a T-cell co-inhibitor.
 22. The multi-specific antigen-binding molecule or fragment thereof of claim 20 or 21, wherein the first antigen-binding specificity comprises three heavy chain CDRs (HCDR1, HCDR2 and HCDR3) contained within any one of the HCVR sequences listed in Table 1; and three light chain CDRs (LCDR1, LCDR2 and LCDR3) contained within any one of the LCVR sequences listed in Table
 1. 23. The multi-specific antigen-binding molecule or fragment thereof of any one of claims 20-22, wherein the first antigen-binding specificity comprises a HCVR having an amino acid sequence selected from the group consisting of HCVR sequences listed in Table 1; and a LCVR having an amino acid sequence selected from the group consisting of LCVR sequences listed in Table
 1. 24. The multi-specific antigen-binding molecule or fragment thereof of claim 23, wherein the first antigen-binding specificity comprises a HCVR/LCVR amino acid sequence pair selected from the group consisting of SEQ ID NOs: 130/138, 162/170, 234/202, and 314/186.
 25. The multi-specific antigen-binding molecule or fragment thereof of claim 21, wherein the second antigen-binding specificity binds specifically to a T-cell co-inhibitor selected from the group consisting of LAGS, TIM3, B7-1, CTLA-4, BTLA, CD28, 2B4, LY108, TIGIT, ICOS, and CD160.
 26. The multi-specific antigen-binding molecule or fragment thereof of any one of claims 20-25 for use in the treatment of a cancer selected from the group consisting of renal cell carcinoma, colorectal cancer, ovarian cancer, prostate cancer, breast cancer, colon cancer, non-small-cell lung cancer and melanoma.
 27. The multi-specific antigen-binding molecule or fragment thereof any one of claims 20-25 for use in the treatment of a chronic viral infection caused by a virus selected from the group consisting of human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV), human papilloma virus (HPV), lymphocytic choriomeningitis virus (LCMV), and simian immunodeficiency virus (SIV).
 28. A multi-specific antigen-binding molecule or fragment thereof comprising a first antigen-binding specificity that binds specifically to PD-1 and a second antigen-binding specificity that binds specifically to an antigen selected from the group consisting of an autoimmune-tissue-specific antigen, a T-cell receptor and an Fc receptor.
 29. The multi-specific antigen-binding molecule or fragment thereof of claim 28, wherein the first antigen-binding specificity comprises three heavy chain CDRs (HCDR1, HCDR2 and HCDR3) contained within any one of the HCVR sequences listed in Table 1; and three light chain CDRs (LCDR1, LCDR2 and LCDR3) contained within any one of the LCVR sequences listed in Table
 1. 30. The multi-specific antigen-binding molecule or fragment thereof of claim 28 or 29, wherein the first antigen-binding specificity comprises a HCVR having an amino acid sequence selected from the group consisting of HCVR sequences listed in Table 1; and a LCVR having an amino acid sequence selected from the group consisting of LCVR sequences listed in Table
 1. 31. The multi-specific antigen-binding molecule or fragment thereof of claim 30, wherein the first antigen-binding specificity comprises a HCVR/LCVR amino acid sequence pair selected from the group consisting of SEQ ID NOs: 130/138, 162/170, 234/202, and 314/186.
 32. The multi-specific antigen-binding molecule or fragment thereof of claim 28, wherein the first antigen-binding specificity comprises the extracellular domain of PD-L1 and/or PD-L2 or fragment thereof.
 33. The multi-specific antigen-binding molecule or fragment thereof of any one of claims 28-32, wherein the second antigen-binding specificity binds specifically to an autoimmune-tissue-specific antigen.
 34. The multi-specific antigen-binding molecule or fragment thereof of claim 33, wherein the autoimmune-tissue-specific antigen is associated with alopecia areata, autoimmune hepatitis, celiac disease, Graves' disease, Guillain-Barre syndrome, Hashimoto's disease, hemolytic anemia, inflammatory bowel disease, inflammatory myopathies, multiple sclerosis, primary biliary cirrhosis, psoriasis, rheumatoid arthritis, scleroderma, Sjögren's syndrome, systemic lupus erthyematosus, vitiligo, autoimmune pancreatitis, autoimmune urticaira, autoimmune thrombocytopenic purpura, Crohn's disease, diabetes type I, eosinophilic fasciitis, eosinophilic enterogastritis, Goodpasture's syndrome, myasthenia gravis, psoriatic arthritis, rheumatic fever, ulcerative colitis, vasculitis or Wegener's granulomatosis.
 35. The multi-specific antigen-binding molecule or fragment thereof of any one of claims 28-32, wherein the second antigen-binding specificity binds specifically to one of a T-cell receptor, Fcα receptor, Fcγ receptor, or CD19.
 36. The multi-specific antigen-binding molecule or fragment thereof of any one of claims 28-35 for use in the treatment of an autoimmune disease or disorder selected from the group consisting of alopecia areata, autoimmune hepatitis, celiac disease, Graves' disease, Guillain-Barre syndrome, Hashimoto's disease, hemolytic anemia, inflammatory bowel disease, inflammatory myopathies, multiple sclerosis, primary biliary cirrhosis, psoriasis, rheumatoid arthritis, scleroderma, Sjögren's syndrome, systemic lupus erthyematosus, vitiligo, autoimmune pancreatitis, autoimmune urticaria, autoimmune thrombocytopenic purpura, Crohn's disease, diabetes type I, eosinophilic fasciitis, eosinophilic enterogastritis, Goodpasture's syndrome, myasthenia gravis, psoriatic arthritis, rheumatic fever, ulcerative colitis, vasculitis and Wegener's granulomatosis.
 37. A method of enhancing an immune response in a subject, the method comprising administering a pharmaceutical composition comprising an isolated antibody or antigen-binding fragment thereof according to any one of claims 1-13; or a multi-specific antigen-binding molecule or fragment thereof according to any one of claims 20-25.
 38. A method of inhibiting a T-regulatory (Treg) cell in a subject comprising administering a pharmaceutical composition comprising an isolated human antibody or antigen-binding fragment thereof according to any one of claims 1-13; or a multi-specific antigen-binding molecule or fragment thereof according to any one of claims 20-25.
 39. A method of enhancing T-cell activation in a subject, the method comprising administering a pharmaceutical composition comprising an antibody or antigen-binding fragment thereof according to any one of claims 1-13; or a multi-specific antigen-binding molecule or fragment thereof according to any one of claims 20-25.
 40. The method of any one of claims 37-39, wherein the subject has a disease or disorder selected from the group consisting of brain cancer, renal cell carcinoma, ovarian cancer, prostate cancer, colon cancer, non-small-cell lung cancer, squamous cell carcinoma of head and neck, colorectal cancer, and melanoma.
 41. The method of any one of claims 37-39, wherein the subject has a chronic viral infection caused by a virus selected from the group consisting of HIV, HCV, HBV, HPV, LCMV and SIV.
 42. A method of inhibiting growth of a tumor or a tumor cell comprising contacting the tumor or tumor cell with a therapeutically effective amount of the antibody of any one of claim 1-13 or 20-25.
 43. A method of inhibiting T-cell activation in a subject, the method comprising administering a therapeutically effective amount of an antibody or antigen-binding fragment thereof according to any one of claims 1-13; or a multi-specific antigen-binding molecule or fragment thereof according to any one of claims 28-35.
 44. The method of claim 43, wherein the subject has an autoimmune disease or disorder selected from the group consisting of alopecia areata, autoimmune hepatitis, celiac disease, Graves' disease, Guillain-Barre syndrome, Hashimoto's disease, hemolytic anemia, inflammatory bowel disease, inflammatory myopathies, multiple sclerosis, primary biliary cirrhosis, psoriasis, rheumatoid arthritis, scleroderma, Sjögren's syndrome, systemic lupus erthyematosus, vitiligo, autoimmune pancreatitis, autoimmune urticaria, autoimmune thrombocytopenic purpura, Crohn's disease, diabetes type I, eosinophilic fasciitis, eosinophilic enterogastritis, Goodpasture's syndrome, myasthenia gravis, psoriatic arthritis, rheumatic fever, ulcerative colitis, vasculitis and Wegener's granulomatosis.
 45. The method of any one of claims 37-44, wherein the antibody or antigen-binding fragment thereof, or the pharmaceutical composition comprising the antibody or antigen-binding fragment thereof, is administered to the subject in combination with a second therapeutic agent.
 46. The method of claim 45, wherein the second therapeutic agent is selected from the group consisting of a NSAID, a corticosteroid, an antibody to a different T-cell co-inhibitor, an antibody to a tumor specific antigen, an antibody to an autoimmune tissue antigen, an antibody to a virally-infected-cell antigen, an antibody to PD-L1, a dietary supplement such an antioxidant, a VEGF antagonist, a chemotherapeutic agent, a cytotoxic agent, an anti-viral drug, radiation, and any other therapy useful for ameliorating at least one symptom associated with the disease or disorder.
 47. The method of any one of claims 37-46, wherein the antibody or antigen-binding fragment thereof is administered subcutaneously, intravenously, intradermally, intraperitoneally, orally, intramuscularly or intracranially.
 48. The method of any one of claims 37-47, wherein the antibody or antigen-binding fragment is administered at a dose of about 0.1 mg/kg of body weight to about 60 mg/kg of body weight of the subject.
 49. The isolated antibody or antigen-binding fragment of claim 1, wherein the antibody or antigen-binding fragment thereof competes for binding to human PD-1 with a reference antibody or antigen-binding fragment thereof comprising a heavy chain and a light chain, wherein the heavy chain comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 330, 332, 334 and
 336. 50. The isolated antibody or antigen-binding fragment of claim 1, wherein the antibody or antigen-binding fragment thereof competes for binding to human PD-1 with a reference antibody or antigen-binding fragment thereof comprising a heavy chain and a light chain, wherein the light chain chain comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 331, 333, 335 and
 337. 51. The isolated antibody or antigen-binding fragment of claim 1, wherein the antibody or antigen-binding fragment thereof competes for binding to human PD-1 with a reference antibody or antigen-binding fragment thereof comprising a heavy chain/light chain amino acid sequence pair selected from the group consisting of SEQ ID NOs: 330/331, 332/333, 334/335 and 336/337.
 52. A pharmaceutical composition comprising an isolated monoclonal antibody or antigen-binding fragment thereof that binds PD-1 according to any one of claims 49-51, and a pharmaceutically acceptable carrier or diluent.
 53. An isolated polynucleotide molecule comprising a polynucleotide sequence that encodes a heavy chain of an antibody as set forth in any one of claims 49-51.
 54. An isolated polynucleotide molecule comprising a polynucleotide sequence that encodes a light chain of an antibody as set forth in any one of claims 49-51.
 55. A vector comprising the polynucleotide sequence of claim 53 or
 54. 56. A cell expressing the vector of claim
 55. 